The misuses of HTML frames

HTML framesets have some good uses, such as including third-party content. They also have misuses, such as disguising third-party involvement.

Recently I needed to set up domain forwarding for a subdomain registered with Godaddy. (The choice of registrar wasn’t my fault.) A couple of options were available, including one that claimed to guarantee that the subdomain would persist through navigation in the address bar. That sounded like a good thing, so I picked it.

At first it seemed to work fine; but when I tried to use the URL of an image on the site, there were weird errors. I soon found out what was going on: Godaddy was wrapping every page referenced by the subdomain in a frameset! This looks like a duck and clicks like a duck, but it isn’t one, and anything that tries to treat HTML as a JPEG file isn’t going to work very well.

Stack Overflow has several reports of people being bitten by this:

Frame wrapping is a good-enough solution for some cases, but when you aren’t told it’s happening, that’s a seriously wrong way to do it. It’s also a security concern, since your domain points at an IP address that you don’t control, and only indirectly at your own site.

This is a blog on file formats, not on irresponsible domain registrars, so the moral here is to realize that framesets aren’t a completely transparent way to provide third-party content. It’s fine to use them, but only if you’re aware that the frameset host and the frame provider are active partners.

The return of music DRM?

U2, already the most hated band in the world thanks to its invading millions of iOS devices with unsolicited files, isn’t stopping. An article on Time‘s website tells us, in vague terms, that

Bono, Edge, Adam Clayton and Larry Mullen Jr believe so strongly that artists should be compensated for their work that they have embarked on a secret project with Apple to try to make that happen, no easy task when free-to-access music is everywhere (no) thanks to piracy and legitimate websites such as YouTube. Bono tells TIME he hopes that a new digital music format in the works will prove so irresistibly exciting to music fans that it will tempt them again into buying music—whole albums as well as individual tracks.

It’s hard to read this as anything but an attempt to bring digital rights management (DRM) back to online music distribution. Users emphatically rejected it years ago, and Apple was among the first to drop it. You haven’t really “bought” anything with DRM on it; you’ve merely leased it for as long as the vendor chooses to support it. People will continue to break DRM, if only to avoid the risk of loss. The illegal copies will offer greater value than legal ones.

It would be nice to think that what U2 and Apple really mean is just that the new format will offer so much better quality that people will gladly pay for it, but that’s unlikely. Higher-quality formats such as AAC have been around for a long time, and they haven’t pushed the old standby MP3 out of the picture. Existing levels of quality are good enough for most buyers, and vendors know it.

Time implies that YouTube doesn’t compensate artists for their work. This is false. They often don’t bother with small independent musicians, though they will if they’re reminded hard enough (as Heather Dale found out), but it’s hard to believe that groups with powerful lawyers, such as U2, aren’t being compensated for every view.

DRM and force-feeding of albums are two sides of the same coin of vendor control over our choices. This new move shouldn’t be a surprise.

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Best viewed with a big-name browser

A few websites refuse to present content if you use a browser other than one of the four or so big-name ones.

An "unsupported browser" message from Apple's support website

The example shown is what I got when I accessed Apple’s support site with iCab, a relatively obscure browser which I often use. Many of Google’s pages also refuse to deliver content to iCab.

There is a real problem that JavaScript isn’t standardized, and it’s necessary to test with each browser to be confident that a page will work properly. However, if a page sticks with the basics of JavaScript and isn’t trying to do animations, video, or other cutting-edge effects, then any reasonably up-to-date implementation of JavaScript should be able to handle it. It’s reasonable to display a warning if the browser is an untested one, but there’s no reason to block it.

Browsers can impersonate other browsers by setting the User-Agent header, and small-name browsers usually provide that option for getting around these problems. After a couple of tries with iCab, I was able to get through by impersonating Safari. Doing this also has an advantage for privacy; identifying yourself with a little-used browser can greatly contribute to unique identification when you may want anonymity. From the standpoint of good website practices, though, a site shouldn’t be locking browsers out unless there’s an unusual need. Web pages should follow standards so that they’re as widely readable as possible. This is especially important with a “contact support” page.

Apple and Google both are browser vendors. Might we look at this as a way to make entry by new browsers more difficult?

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The animated GIF is the new blink tag

In the early days of HTML, the most hated tag was the <blink> tag, which made text under it blink. There were hardly any sensible uses for it, and a lot of browsers now disable it. I just tested it in this post, and WordPress actually deleted the tag from my draft when I tried to save it. (I approve!)

Today, though, the <blink> tag isn’t annoying enough. Now we have the animated GIF. It’s been around since the eighties, but for some reason it’s become much more prevalent recently. It’s the equivalent of waving a picture in your face while you’re trying to read something.

I can halfway understand it when it’s done in ads. Advertisers want to get your attention away from the page you’re reading and click on the link to theirs. What I don’t understand is why people use it in their own pages and user icons. It must be a desire to yell “Look how clever I am!!!” over and over again as the animation cycles.

Fortunately, some browsers provide an option to disable it. Firefox used to let you stop it with the ESC key, but last year removed this feature.

If you think that your web page is boring and adding some animated GIFs is just what’s needed to bring back the excitement — Don’t. Just don’t.

Update: I just discovered that a page that was driving me crazy because even disabling animated GIFs wouldn’t stop it was actually using the <marquee> tag. I believe that tag is banned by the Geneva Convention.

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Canvas fingerprinting, the technical stuff

The ability of websites to bypass privacy settings with “canvas fingerprinting” has caused quite a bit of concern, and it’s become a hot topic on the Code4lib mailing list. Let’s take a quick look at it from a technical standpoint. It is genuinely disturbing, but it’s not the unstoppable form of scrutiny some people are hyping it as.

The best article to learn about it from is “Pixel Perfect: Fingerprinting Canvas in HTML5,” by Keaton Mowery and Hovav Shacham at UCSD. It describes the basic technique and some implementation details.

Canvas fingerprinting is based on the <canvas> HTML element. It’s been around for a decade but was standardized for HTML5. In itself, <canvas> does nothing but define a blank drawing area with a specified width and height. It isn’t even like the <div> element, which you can put interesting stuff inside; if all you use is unscripted HTML, all you get is some blank space. To draw anything on it, you have to use JavaScript. There are two APIs available for this: the 2D DOM Canvas API and the 3D WebGL API. The DOM API is part of the HTML5 specification; WebGL relies on hardware acceleration and is less widely supported.

Either API lets you draw objects, not just pixels, to a browser. These include geometric shapes, color gradients, and text. The details of drawing are left to the client, so they will be drawn slightly differently depending on the browser, operating system, and hardware. This wouldn’t be too exciting, except that the API can read the pixels back. The getImageData method of the 2D context returns an ImageData object, which is a pixel map. This can be serialized (e.g., as a PNG image) and sent back to the server from which the page originated. For a given set of drawing commands and hardware and software configuration, the pixels are consistent.

Drawing text is one way to use a canvas fingerprint. Modern browsers use a programmatic description of a font rather than a bitmap, so that characters will scale nicely. The fine details of how edges are smoothed and pixels interpolated will vary, perhaps not enough for any user to notice, but enough so that reading back the pixels will show a difference.

However, the technique isn’t as frightening as the worst hype suggests. First, it doesn’t uniquely identify a computer. Two machines that have the same model and come from the same shipment, if their preinstalled software hasn’t been modified, should have the same fingerprint. It has to be used together with other identifying markers to narrow down to one machine. There are several ways for software to stop it, including blocking JavaScript from offending domains and disabling part or all of the Canvas API. What gets people upset is that neither blocking cookies nor using a proxy will stop it.

Was including getImageData in the spec a mistake? This can be argued both ways. Its obvious use is to draw a complex canvas once and then rubber-stamp it if you want it to appear multiple times; this can be faster than repeatedly drawing from scratch. It’s unlikely, though, that the designers of the spec thought about its privacy implications.

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Cookbooks vs. learning books

A contract lead got me to try learning more about a technology which the client needs. Working from an e-book which I already had, I soon was thinking that it’s a really confused, ad hoc library. But then I remembered having this feeling before, when the problem was really the book. I looked for websites on the software and found one that explained it much better. The e-book had a lot of errors, using JavaScript terminology incorrectly and its own terminology inconsistently.

A feeling came over me, the same horrified realization the translator of To Serve Man had: “It’s a cookbook!” It wasn’t designed to let you learn how the software works, but to get you turning out code as quickly as possible. There are too many of these books, designed for developers who think that understanding the concepts is a waste of time. Or maybe the fault belongs less to the developers than to managers who want results immediately.

A book that introduces a programming language or API needs to start with the lay of the land. What are its basic concepts? How is it different from other approaches? It has to get the terminology straight. If it has functions, objects, classes, properties, and attributes, make it clear what each one is. There should be examples from the start, so you aren’t teaching arid theory, but you need to follow up with an explanation.

If you’re writing an introduction to Java, your “Hello world” example probably has a class, a main() function, and some code to write to System.out. You should at least introduce the concepts of classes, functions, and importing. That’s not the place to give all the details; the best way to teach a new idea is to give a simple version at first, then come back in more depth later. But if all you say is “Compile and run this code, and look, you’ve got output!” then you aren’t doing your job. You need to present the basic ideas simply and clearly, promise more information later, and keep the promise.

Don’t jump into complicated boilerplate before you’ve covered the elements it’s made of. The point of the examples should be to teach the reader how to use the technology, not to provide recipes for specific problems. The problem the developer has to solve is rarely going to be the one in the book. They can tinker with the examples until they fit their own problem, not really understanding them, but that usually results in complicated, inefficient, unmaintainable code.

Expert developers “steal” code too, but we know how it works, so we can take it apart and put it back together in a way that really suits the problem. The books we can learn from are the ones that put the “how it works” first. Cookbooks are useful too, but we need them after we’ve learned the tech, not when we’re trying to figure it out.

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HTML and fuzzy validity

Andy Jackson wrote an interesting post on the question of HTML validity. Only registered Typepad users can comment, so it’s easier for me to add something to the discussion here.

When I worked on JHOVE, I had to address the question of valid HTML. A few issues are straightforward; the angle brackets for tags have to be closed, and so do quoted strings. Beyond that, everything seems optional. There are no required elements in HTML, not even html, head, or body; a blank file or a plain text file with no tags can be a valid HTML document. The rules of HTML are designed to be forgiving, which just makes it harder to tell if a document is valid or not. I’ve recommended that JHOVE users not use the HTML module; it’s time-consuming and doesn’t give you much useful information.

There are things in XHTML which aren’t legal in HTML. The “self-closing” tag (<tag/>) is good XHTML, but not always legal HTML. In HTML5, <input ... /> is legal, but <span ... /> isn’t, because input doesn’t require a closing tag but span does. (In other words, it’s legal only when it’s superfluous.) However, any recent browser will accept both of them.

The set of HTML documents which are de facto acceptable and unambiguous is much bigger than the set which is de jure correct. Unfortunately, the former is a fuzzy set. How far can you push the rules before you’ve got unsafe, ambiguous HTML? It depends on which browsers and versions you’re looking at, and how strenuous your test cases are.

The problem goes beyond HTML proper. Most browsers deal with improper tag nesting, but JavaScript and CSS can raise bigger issues. These are very apt to have vendor-specific features, and they may have major rendering problems in browsers for which they weren’t tested. A document with broken JavaScript can be perfectly valid, as far as the HTML spec is concerned.

It’s common for JavaScript to be included by an external reference, often on a completely different website. These scripts may themselves have external dependencies. Following the dependency chain is a pain, but without them all the page may not work properly. I don’t have data, but my feeling is that far more web pages are broken because of bad scripts and external references than because of bad HTML syntax.

So what do you do when validating web pages? Thinking of it as “validating HTML” pulls you into a messy area without addressing some major issues. If you insist on documents that are fully compliant with the specs, you’ll probably throw out more than you accept, without any good reason. But at the same time, unless you validate the JavaScript and archive all external dependencies, you’ll accept some documents that have significant preservation issues.

It’s a mess, and I don’t think anyone has a good solution.

Update: Andy Jackson has written a post responding to this, Web Archiving in the JavaScript Age.

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OOXML: The good and the bad

An article by Markus Feilner presents a very critical view of Microsoft’s Open Office XML as it currently stands. There are three versions of OOXML — ECMA, Transitional, and Strict. All of them use the same extensions, and there’s no easy way for the casual user to tell which variant a document is. If a Word document is created on one computer in the Strict format, then edited on another machine with an older version of Word, it may be silently downgraded to Transitional, with resulting loss of metadata or other features.

On the positive side, Microsoft has released the Open XML SDK as open source on Github. This is at least a partial answer to Feilner’s complaint that “there are no free and open source solutions that fully support OOXML.”

Incidentally, I continue to hate Microsoft’s use of the deliberately confusing term “Open XML” for OOXML.

Thanks to @willpdp for tweeting the links referenced here.

The uses and abuses of PDF

PDF is a versatile format, but that doesn’t mean it should be used for everything. It’s a visual presentation format above all else. It lets you define a document with a specific appearance, with capabilities such as form filling and text searching. It’s not very good if you want a document that adapts to different device capabilities. If you need an editable format or a way to deliver structured data, there are much better alternatives.

When the Malaysian government released satellite data from the communications of Flight 370, which had disappeared, it delivered a PDF file. It looks very nice, but anyone who wants to extract and analyze the data has to do a lot of extra work. A spreadsheet or structured text (e.g., CSV) document is the right thing.

PDF can be used for e-books, but it’s not ideal. If you create normal sized pages, then on a phone they’ll either look tiny or require a lot of scrolling. Formats such as EPUB work better with a range of screen sizes.

Delivering text documents in PDF loses a lot of its value when the document is a scanned image rather than a text-based document. It can’t be searched, and people with visual disabilities can’t use text-to-speech. My condo association delivers its newsletters in scanned-image PDF. When I pointed out these problems at an owners’ meeting, I was told that the owners weren’t sophisticated enough to take advantage of those benefits. Our complex is a big one, and I’d be surprised if at least a few residents don’t use text-to-speech when they can. It’s not particularly hard to generate PDF files; scanning a finished document into a PDF seems like the hard way.

To maximize the usefulness of assistive technologies, you should create PDF/A if possible. It produces a slightly larger file, but it’s organized in a way that makes extraction of content easier and eliminates dependencies you might not have thought of.

Redacting PDFs is another tricky issue. If you simply black out an area, that’s the equivalent of gluing a piece of paper over it, and no harder to defeat. For advice on properly redacting documents, who better to turn to than the NSA? They may be a gang of criminals within the government, but they certainly know how to redact. It’s from 2006, though, so some of its advice could be dated.

There are lots of things you can do with PDF, but use it intelligently and where it’s appropriate.

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