So you have a website but where is it on Google? Have you fallen foul of a penalty or have you overlooked one of the many common search engine optimisation pitfalls when designing your site?

Understanding what works for the search engines and what doesn't when it comes to the content on your website can have a crucial impact on the relevance and/or page rank of your pages from a SEO perspective.

Here we highlight common mistakes that could affect your ranking on Google and other search engines.

Optimising for the correct keywords - Basically 'Get real' about what keywords you feel your website can be ranked for. If you have a ten page website in a highly competitive market then ranking naturally for the major terms will be close to impossible. Use the Overture keyword tool together with the number of results on Google to find out what keywords are searched for and how many other websites are targeting them. If you are lucky then you might even find a popular keyword that not many other websites are optimised for. Alternatively a good tool for this job is Wordtracker from Rivergold Associates Ltd.

Code validation - If your html code is not valid then this could make it very difficult or even impossible for a search engine to separate your page content from your code. If the search engine cannot see your content then your page will obviously have no relevance.

Frames - Even though most, if not all, major search engines now index frames and even with the use of the NOFRAMES tag you run the risk of your pages being displayed in the search engine results out of context. As each individual page is indexed separately, it is likely that your website visitors will not see your pages within your frame and will effectively be stuck on the page they arrive at.

If you must use frames then create a 'Home' link on each of your individual content pages and point the link at your frameset index page.

JavaScript navigation - If you use JavaScript to control your website navigation then search engine spiders may have problems crawling your site. If you must use JavaScript then there are two options available to you:

Use the NOSCRIPT tag to replicate the JavaScript link in standard HTML. Replicate your JavaScript links as standard HTML links in the footer of your page.

Flash content - Currently only Google can index Macromedia Flash files, how much or how little content they see is open to debate. So until search engine technology is able to handle your .swf as standard then it would be advisable to avoid the use of these. Again if you must use Flash then offer a standard HTML alternative within NOEMBED tags.

Dynamic URLs - Although Google and Yahoo are able to crawl complicated URLs it is still advisable to keep your URLs simple and avoid the use of long query strings. Do not including session IDs in the URL as these can either create a 'spider trap' where the spider indexes the page over and over again or, at worst, your pages will not get indexed at all. If you do need to include parameters in the URL then limit them to two and the number of characters per parameter to ten or less.

The best SEO solution for dynamic URLs is to use Mod-rewrite or Multiviews on Apache.

No sitemap - A sitemap is the search engine optimisation tool of choice to ensure every page within your website is indexed by all search engines. You should link to your site map from, at least, your homepage but preferably from every page on your website. If your website contains hundreds of pages then split the sitemap into several categorised maps and link these all together. Try and keep the number of links per page on a sitemap to less than 100.

Excessive links - Excessive links on a given page (Google recommends having no more than 100) can lower its relevance and, although it does not result in a ban, this does nothing for your search engine optimisation strategy.

Be careful who you link to - As you have no control over who links to your website, incoming links will not harm your rank. However outbound links from your website to 'bad neighbourhoods' like link farms will harm your ranking.

As a rule ensure as many of your outbound links as possible link to websites that are topical to your field of business.