Get rid of Session IDs
Many sites that track users or have special session specific features have Session ID's turned on to use in identifying visitors. A lot of Ecommerce sites use Session ID's.
Whilst these work very well at making sure only that user session can access specific data, they do cause problems for search engines. You will often see a result in a search engine with a PHP Session ID in the URL as a parameter. Clicking on this result very often takes you to an incorrect or unavailable page.
The reason this happens is that when the search engine spider visited the page and indexed it, the spider got its own unique Session ID. Thats great but guess what? You session doesn't match the Session ID so you don't get the same page! Quite often this is a blank or unavailable page.
Not only is this annoying, when the search engine comes back to the same URL with the origional Session ID parameter, that session will quite likely have expired so it too will get a blank page. This can be quite detrimental to search engines.
Whilst the need to determine session verification is obvious from a security point of view, it doesn't help us much when we need our Ecommerce site to rank in search egines.
Well there is a solution! You can turn this off so it is not displayed in the URL and there is a useful method of storing Session Headers that are not displayed in the URL but work in much the same way. So there you have it, the best of both worlds!
The SEO Files Recomends
The SEO Files recomends that you turn off Session IDs in your URLs so search engines and users can see the same content.