Definition: Certain characters, such as ampersand (&), equals sign (=), and question mark (?), when in a web page’s URL, tip off a search engine that the page in question is dynamic. Search engines are cautious of indexing dynamic pages for fear of spider traps, thus pages that contain stop characters in their URL run the risk of not getting indexed and becoming part of the “Invisible Web.” Google won’t crawl more than one dynamic level deep. So dynamic pages with stop characters in its URL should get indexed if a static page links to it. Eliminating stop characters from all URLs on your site will go a long way in ensuring that your entire site gets indexed by Google.
FirstClickSEO Commentary: This is why your Web site coding must be very clean and professional.