Google recently announced that they’ve made a change to their algorithm that now permits a parameter that is commonly used in the URLs of dynamic websites. On the Official Google Webmaster Central Blog, Venessa Fox stated:
Don’t use “&id=” as a parameter in your URLs, as we don’t include these pages in our index.
However, we’ve recently removed that technical guideline, and now index URLs that contain that parameter. So if your site uses a dynamic structure that generates it, don’t worry about rewriting it — we’ll accept it just fine as is. Keep in mind, however, that dynamic URLs with a large number of parameters may be problematic for search engine crawlers in general, so rewriting dynamic URLs into user-friendly versions is always a good practice when that option is available to you. If you can, keeping the number of URL parameters to one or two may make it more likely that search engines will crawl your dynamic urls.
As Venessa said, it’s still best to create search engine friendly URLs. Not only is better for Googlebot, it’s also better for search engine optimization (SEO). Google’s search engine results algorithm takes into account the words that are used in the URL.
The ideal search engine friendly URL has keywords in the address and uses hyphen to separate multiple words. e.g. http://dogs.com/tutorials/washing-dirty-dogs/ . You shouldn’t use underscores between words, because Google will count it as a phrase and will ignore the individual weight of each word.