There was a time when Internet Explorer was arguably all anyone needed by way of a browser. By being ubiquitous, Microsoft almost managed to quash its competition entirely, and other browsers were the thing of geeks and Mac users. Why would not someone use IE? You bought a computer, it came with Windows, and when you needed a browser, well, there was IE, already installed and configured.
Back in these dark ages, as a web designer, you really only needed to use Internet Explorer to test your sites. You might want to pull it up on Netscape Navigator if you wanted to be really complete, but as long as it looked good at least 90% of your target audience was going to see exactly what you were seeing .
But now the browser market has changed. Where once the idea of bothering with anything other than IE was unthinkable, now more and more people are turning to various options. Firefox, of course, leads the way. But let's not forget the growing Apple market share; all those new iMacs and MacBooks running Safari as their default browser. And then, of course, there's Opera, always flagging behind but reflecting a wildly devoted following who hate nothing more than to find your site does not work in their browser of choice.
And that still leaves Camino, OmniWeb, Netscape Navigator, as well as countless independent and Open Source browsers. Run a search on 'browser download' through Google and you get over 350,000,000.
And it does not help that Internet Explorer is one of the most forgiving browsers out there. A site with a buggy back-end may come up just fine on IE. But trying to view it on anything else is a nightmare. Your professional, attractive site suddenly looks like an introductory HTML lesson gone wrong.
This is why web standards are growing more and more important with each passing day. As more and more browsers begin to get a foothold in the market, there's needed a simple way to make sure your site works on every one of them. These days, any browser worth its salt is now standard's compliant. This means that there is agreed upon a specific set of standards, and as long as everyone plays by the rules, we all get along.
Fortunately, there are sites out there dedicated to promoting web standards and helping web designers in making sure their sites follow these rules. The Web Standards Project offers information and tutorials about incorporating these web standards and why it's important.
And of course, the de facto authority on these standards, the w3c (short for World Wide Web Consortium) offers news, information, and my favorite, an suite of easy-to-use validators to make sure your site is up to snuff. Run your URL or local file through the HTML and CSS validators found there and you'll be able to see at a glance where your site might run into issues. Pass the test with no errors, and they even give you a button you can display on your site to show your visitors that you care about web standards.
Of course, cross-browser compatibility is just one of many reasons to consider using web standards. Standards compliant pages work better with accessible software, they show up clearer to search engines, and they are likely to have a longer shelf life as the web and its browsers evolve.