Google's got a blog post out today (and SELand covers it) about how they now recommend that webmasters and site owners DO NOT rewrite their ugly dynamic URLs to be clean and static. What's the reasoning behind this?

We've come across many webmasters who, like our friend, believed that static or static-looking URLs were an advantage for indexing and ranking their sites. This is based on the presumption that search engines have issues with crawling and analyzing URLs that include session IDs or source trackers. However, as a matter of fact, we at Google have made some progress in both areas. While static URLs might have a slight advantage in terms of clickthrough 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. Providing search engines with dynamic URLs should be favored over hiding parameters to make them look static.

The fundamental problem here is that Google is thinking about this from a completely different perspective as marketers. It's not that they're wrong or lying or creating misinformation, it's just that they're looking out for their best interests - effectively and efficiently crawling the web and serving up accurate data about the contents of pages. When URL rewrites go awry, it can screw up Google's ability to return the results their users want (and as content publishers, the results you want).

However, the fact that some developers incorrectly create rewrite rules does not mean that sticking with dynamic parameters is now the "best practice." It simply means you have to do it right.

Let's go over the list of pros and cons for static vs. dynamic URLs and see what's really changed:

Pros of Dynamic URLs

• Umm... they're usually longer?
• Google (1 of the 4 major search engines) says they can effectively crawl and index them

Cons of Dynamic URLs

• Lower click-through rate in the search results, in emails, and on forums/blogs where they're cut and pasted
• A greater chance of cutting off the end of the URL, resulting in a 404 or other error when copying/pasting
• Lower keyword relevance and keyword prominence
• Nearly impossible to write down manually and share on a business card or read over the phone to a person
• Challenging (if not impossible) to manually remember
• Does not typically create an accurate expectation of what the user will see prior to reaching the page
• Not usable in branding or print campaigns
• Won't typically carry optimized anchor text when used as the link text (which happens frequently due to copying & pasting)

Pros of Static URLs (mostly the opposites of the above)

• Higher click-through rates in the SERPs, emails, web pages, etc.
• Higher keyword prominence and relevancy
• Easier to copy, paste and share on or offline
• Easy to remember and thus, usable in branding and offline media
• Creates an accurate expectation from users of what they're about to see on the page
• Can be made to contain good anchor text to help the page rank higher when linked-to directly in URL format
• All 4 of the major search engines (and plenty of minor engines) generally handle static URLs more easily than dynamic ones, particularly if there are multiple parameters

Cons of Statics URLs

• You might mess up the rewriting process, in which case your users and search engines will struggle to find content properly on your site.

So - bottom line - dynamic URLs don't afford you the same opportunity for search engine rankings, usability or portability that rewritten, keyword-optimized URLs do. Just because one of the engines doesn't have trouble crawling them doesn't mean it's any less critical to continue optimizing this element of a site's structure.

If you buy into Google's argument that because rewriting URLs can occassionally cause problems (nevermind that we've done it at SEOmoz and with our clients dozens of times without issues), you're setting yourself up for something significantly less than search engine "optimization." I'd be tempted to call it conservative SEO, but it's not really even that. It's the mindset that living in fear of change rather than pursuing the best course of action is the better choice, and none of us who do SEO for a living should support that mentality.