Question

I’ve seen a lot of users on this site provide operating system specs when describing web development bugs and I’ve seen a few instances of things working on one OS but not another.

Is there an actual difference in what gets processed by let’s say IE6 on different versions of windows? Or the exact same version of firefox on ubuntu as opposed to mac?

This may be a noob question, but I’m really curious.

Answer 1

There are essentially 4 categories of cross-OS bugs that can occur in website (unintentionally; ignoring things like the web developer sniffing the user agent and screwing with unrecognized results, or using a plugin that can only work on one platform, such as Silverlight). Ordered in the most-common to least-common, from my personal experience

1. Assumptions about fonts and kerning — If the user’s operating system does not match your own, and you specify a font that your system has that theirs does not, the text will not have exactly the same length and possibly height, even when specifying a specific point size (the lowercase ‘m’ should match, but all other characters can differ, like the height of the capitals). This can wreak havoc on fixed-sized layouts, especially with headings that are expected to be only one line long. Lately, this can be mitigated by buying a “webfont” (usually both old IE and the new modern standard web font are included) and using that in your CSS, hosting the font for the user to download. This can produce a “flash” as the rendering is switched to it once downloaded, though, so you definitely need to specify a long caching time.
2. Assumptions about form elements — Since these HTML elements are created by the operating system directly, rather than by the browser, even for the same browser they can look different, have different sizes and behaviors, between operating systems. Styling these elements reduces the variability, but some of the form elements (like the <input type="file">) cannot be styled. Just give them a large buffer in your layout.
3. Buggy plugins — Even if the plugin exists across all operating systems, like Flash, generally they work best on Windows, and then Linux and Mac fight it out for second place (usually more effort put into the Mac port, but on Linux there may be Wiki guides to get it working better, and the distro packagers may use these tricks when auto-installing the plugin for you). The only solution I know is, if you’re a Windows dev, to have a VirtualBox image of a Linux distro like Ubuntu or Fedora that you test your site on, and see how poor the plugin performs when you add all of your bells and whistles, then assume that Macs are roughly the same performance.
4. Actual bugs in the HTML renderer — These can happen, and as the pace of browser development is increasing, the feature/bug parity gap is widening between platforms. Generally, the “native” OS of the browser does the best, followed by whichever platform uses it the most after that. I rarely see regressions, so once something is working across all OSes for a browser, it basically stays that way. You have to be doing something real special to run into this.