Indexing Obstacles for Dynamic Web Sites
URL Parameters, Session ID’s, Reserved Characters and Deep Nested web pages can make it harder for search engines to fully index your website. If your site uses any of the following you may find it hard to get indexed by the search engines:
Parameters
If your URL’s include parameters (end with ?a=1&b=2) then the search engines may not index these pages. This is because the spider can get caught in an infinite loop, indexing the same page hundreds of times with exactly the same content.
It used to be that no search engines would index pages with parameters. This is now much improved to how it used to be, however to ensure your site is indexed by all the search engine spiders always limit to a maximum of two parameters, but if possible use none.… Read the rest