Overview: Search engines will often take a snapshot of your website, so it's important to present your most relevant content on the top of your pages in case search engines don't spider your entire page.

Some search engines that spider a website often take a quick snapshot of your webpage, or rather a quick overview of the content located at the top of your website. Smaller search engines don't have the physical resources to index millions of complete webpages, so rather they rely on the most relevant data which is usually located on the main page and towards the top of the page. Even those search engines which do index the entire full text often weigh relevancy and priority on the top portion.

Consequently, you should place as much relevant information towards the beginning of your page(s). Search engines that will index a description about your website will either use META Tag descriptions or the first few lines of text in your documents. If you have any javascripts or imagemap definitions, try to push them towards the bottom of your webpage as you don't want search engines placing priority on the code behind your scripts rather than relevant content.

Content Order Before
Header
Scripts
Body
Footer

Content Order After
META Tags
Header
Body
Footer
Scripts

Note: You should also push comments and all relevant content towards the top of the body and all scripts and imagemap code to the bottom of the page

Notes and Comments
META Tags are an important way to control how search engines index your site and how they categorize your webpages, as such you should place META Tags towards the very top, even before the headers load to ensure search engines read them first.

Related Links:
META Tag Generator