What Constitutes a Valid Email Address?

I thought I knew, but it turns out I didn’t.

While searching through the error logs of a multiple locale project at work, I discovered users using accents in their email address, which were failing the system’s validation techniques.
Looking around on the Google, it turns out most people have made the same mistake I did. The actual set of characters allowed for an email address are far greater than I could have ever imagined.

Check out this article on Haacked about the subject.

If you’re keen on making sure your website code is perfect, then make sure you give the W3C’s HTML and CSS validator’s a try. These free web-based tools allow you to check whether your HTML and CSS files conform to the W3C specifications.

The W3C HTML validator allows you to check any online web page or upload an offline HTML page, and will return a detailed list of where your page does not conform to standards.

The W3C CSS validator can check that you have written valid CSS in external CSS stylesheets.

Finally, the W3C Broken Links report will check for any broken links.

If you’re HTML is in a mess (!!!), check out HTMLTidy, which is available both as a web based service and as a Firefox extension. HTMLTidy will remove any empty tags, correct simple errors and indent code nicely to make it more readable.