Google has clarified (and confused some webmasters in the process) how it handles dynamic versus static URLs - will you listen? You'll want to read more if you've spent time rewriting URLs to accommodate user-friendly structures over the years - apparently, in the eyes of Google, it's not necessary.
Google is suggesting not rewriting dynamic URLs as it is difficult for Web designers and developers to create and maintain sites that make the change (if they don't know for certain what they are doing) AND Google itself might have problems crawling and ranking dynamic URLs if they are made to look static (in the process hiding parameters which offer Googlebot valuable information on the content of the page.)
Let's actually backup a bit and provide a little background. Static URLs are those that do not change (they contain no parameters.) If you've ever undertaken an effort to rewrite dynamic URLs you know how that goes. Updating these pages can be tedious and time consuming, especially if there is a large quantity of information behind the scenes, which is why so many turn to rewriting dynamic URLs - wherein content is pulled from a database and displayed in a restructured fashion on-demand.
You might want to review a few articles previously published on Website Magazine as background.
Ask the Experts: Rewriting Looooong URLs
How-to Guide: Redirects and htaccess
By all accounts and by Google's own admission, it is safer to serve the dynamic URL and let Google manage detecting/avoiding problematic parameters. Why? The commonly held belief that static or static-looking URLs are an advantage for indexing and ranking sites no longer applies. In the past, Google (as did all search engines - that continues by the way) had problems with session ID's and parameters. Progress has been made over time however, so now (according to Google) "While static URLs might have a slight advantage in terms of click through rates because users can easily read the URLs, the decision to use database-driven websites does not imply a significant disadvantage in terms of indexing and ranking." In short, providing search engines with dynamic URLs should be favored over hiding parameters to make them look static.
As you can imagine, the announcement is causing great amount of confusion in SEO circles. For those using WordPress permalinks, if you can be certain that they do not introduce any irrelevant elements into the URL (which WordPress is actually very good at producing) then there should not be any problems. For those using SEO modules that rewrite URLs (like the ones we featured last week), know in no uncertain terms that Google prefers the dynamic URLs as these solutions make understanding a website easier - for Google.
While Google may claim that they can now properly handle dynamic URLs as well as they handle static URLs, I would advise that you continue to use rewrite to create static-looking URLs for users - not the search engines themselves. If you do decide to not rewrite URLs, make sure pages are defined by no more than three parameters.
