"Some hints and tips for SE friendly URLs and query strings 1 - donít use Ďidí anywhere in the query string 2 - donít send more than 3 variables in the URL 3 - donít link from one page with a query string to another page with a query string [static to dynamic is indexed, dynamic to static is indexed but dynamic to dynamic is not indexed]"
The items you listed are just standard best practices when using dynamic urls. The "id" usually refers to session ids. SERPS do not like them because if you assign a session id to everyone you are in a sense creating duplicate pages of the same content. This is where the issue with SERPS arises. For example www.example.com/index.asp?id=12345 and www.example.com/index.asp?id=12347 are the same pages, but appear different. <br><br> Limiting the number of variables in a url string is a good practice to keep your URLs clean for SERPS and visitors alike. The more variables you add to your URL string the more difficult it is for spiders to crawl. I will have to note that I have been in the SEM industry for quite awhile and spiders have gotten alot better at crawling more complex URLs and dynamic sites in general.