ronym title="Search Engine Optimisation">SEO is a curse to some who see it as a method of spamming or deceiving search engines to favour your site. This should not be the case, search engine optimisation should consist of making sure you have good, well marked content that has links inbound and outbound.
One of the most important things to remember is to make sure your markup is semantically correct. This is something I've talked to you about before, and will be likely to talk about it again. I really can't emphasise enough how important it is to have well structured code. This means headers should use h1, h2, etc. in the correct order, and should definately pass W3C XHTML 1.1 validation at the very least.
In making sure you site is correctly marked up I'd recommend using various validators and code checkers to ensure code quality.
- W3C Markup (HTML) Validation - validate (X)HTML markup on pages
- W3C CSS Validation - validate your site's CSS
- WDG HTML Validator
Make sure that titles are marked up correctly as headings, and not divs or some other tag that has been styled to look like a title - robots such as googlebot deem headings more important than normal content. One way to see if your page is well marked up is to disable all the styles on the page. In Firefox, with the Web Developer toolbar, this is an easy task as you can disable the CSS from the cSS menu. If you are using some other browser, or don't have the Web Developer's toolbar then just try commenting out the links to the stylesheet. This will give you a good picture of what to change to make your site well structured.
Good quality, semantically correct code is not the only thing that is important - but also making sure it has a good level of accessibility. Not every search engine robot (aka spider / crawler) understands JavaScript, and none will index content that exists inside Flash objects or other similarly embedded objects. Any content that is like this should have a well marked up alternative so that robots, and screen readers can still access the content with no trouble. In order to check the accessibility of your site you can use the Watchfire webXACT tool I mentioned earlier, or use some other tool such as the T.A.W. plugin for Mozilla Firefox.
T.A.W. is an analysis tool based upon the guidelines set by WCAG 1.0 and checks for compliance to the 3 levels of accessibility. For users who do not develop, or do their SEO work in Firefox, there is also an online analysis tool available. It is true the accessibility does not strictly affect the ranking of the site so much as well marked up content with a good keyword density of around 5% - but it is a good excuse to make sure the accessibility of your site is good.
