Creating a Website: The Missing Manual, 3rd Edition

Checking Your Pages for Errors

Even a web designer with the best intentions can write bad markup and break the rules of HTML. Although browsers really should catch these mistakes, virtually none of them do. Instead, they do their best to ignore mistakes and display flawed documents.

At first glance, this seems like a great design—after all, it smoothes over any minor slip-ups you might make. But there’s a dark side to tolerating mistakes. In particular, this behavior makes it all too easy for serious errors to lurk undetected in your web pages. What’s a serious error? A problem that’s harmless when you view the page in your favorite browser, but makes an embarrassing appearance when someone views the page in another browser; a mistake that goes undetected until you edit the code, which inadvertently exposes the problem the next time your browser displays the page; or an error that has no effect on page display but prevents an automated tool (like a search engine) from reading the page.

Fortunately, there’s a way to catch problems like these. You can use a validation tool that reads through your web page and checks its markup. If you use a professional web design tool like Dreamweaver, you can use its built-in error checker (Chapter 4 has the details). If you create pages by hand in a text editor, you can use a free online validation tool.

Here are some potential problems that a validator can catch:

• Missing mandatory elements (for example, the <title> element)

• A start tag without a matching ...