For the uninitiated, Web sites are composed of several major kinds of content. The really exciting stuff are JavaScript, images, videos, Flash, and other multimedia. It's what you notice and what your visitors notice too. But (mostly) the search engines don't notice it at all.

What the search engines mainly notice are two things: your text and your markup. The text is easy enough--you can probably figure out why that's important and how you create and optimize it for search. Write naturally, add a few dollops of keywords, fix up your title and description tags and you've done most of what's important.

But the markup is the boring stuff. The markup is just a set of formatting instructions that tell the Web browser when to make something bold (or blue), when to start a new paragraph or where to place a bullet. You probably wouldn't expect that much could go wrong there, but you would be wrong. Markup languages, such as the HTML (HyperText Markup Language) that define the formatting on a Web page, can be a bit tricky. It's rather easy to make a mistake in your markup, unfortunately.

So what's the big deal? Browsers actually are quite forgiving when it comes to markup errors. They likely render the pages properly regardless of whether you have mistakes. But the search engine spiders are quite a bit more finicky. Those delicate spiders can be thrown off quite easily at times when a page is coded incorrectly. Often, that doesn't do any harm, but sometimes it causes the spider to miss big portions of your page, meaning that all the words in those areas are not indexed and can never cause your page to be found.

Admittedly, this is a rather minor item in the scheme of all things search, so if it was quite difficult to detect or to fix, I might advise you to forget it. But it's extremely easy to detect and almost as easy to fix. A free Web site, called the World Wide Web Consortium (W3C) at w3.org owns and maintains the standards for what makes HTML valid, and hapily they do more than create a book full of rules for that. The W3C offers a free validation tool, called (predictably enough) the W3C Markup Validation Service that you can use to find the errors on any Web page.

So, OK, you can find the errors, but you don't have to be the one to fix them. Just understand that you can really hurt your search results if you have a boatload of errors. A few errors are normal and nothing to worry about, but make sure your Web person takes care of validation or maybe the errors will take care of your search marketing efforts. And not in a good way.