Google’s current webmaster guidelines currently state that:

“If you decide to use dynamic pages (i.e., the URL contains a “?” character), be aware that not every search engine spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and their number few.”

So OK, I understand that not all search engines can spider dynamic pages but want to make sure that Google does as this is my focus.

So lets address some of the issues with dynamic pages and see if Google really does spider these and apply page rank in the same way.

1. Firstly how many is a few parameters? I have heard two things 2 to 3 parameters and 1 to 2 parameters. Back in 2005 Matt Cutts is quoted as saying:

“..you are safe if the number of variables in your URL is one or two, unless one of those two variables is named id (or something else resembling a session ID), in which case all bets are off. “

In 2006 he was quoted as saying:

“You definitely CAN use too many parameters, so I would opt for 2 or 3 at the most, if you have any choice whatsoever.”

So judging by the fact that Google is yet to define exactly how many parameters you should have in your URL then I would conclude that in order to be safe 2 should be the maximum number (Their is still a little vagueness about the 3rd parameter!)

2. In the first quote above Matt Cutts also mentions “all bets are off” in relation to URL’s that resemble session ID’s. So should you be worried if your URL’s still contain something like this? Well until October last year Google had the following line in it’s webmaster guidelines:

“Don’t use “&id=” as a parameter in your URLs, as we don’t include these pages in our index.”
However this was removed in October and Google released an official statement in it’s blog:
“‘[Google now indexes] 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 URL’s.”

So what does this all mean for your dynamic website?

Firstly make sure that your pages only use up to a maximum of 2 parameters. Any more than that and they may not be spidered. Also if you use too many you may have problems with search engine spiders getting caught in a loop and falling down. As a result they may not return to the site to spider it again and this could have an impact of rankings.

Secondly if you have got “ID=” in your URL’s already these pages still may be suffering from when Google didn’t index them. As such you may see no page rank at present as these pages may be treated as brand new ones in the index so you should now see these pages appearing in the index and attaining page rank. A such you should not opt for a URL re-write based solely on this point.

So overall should you re-write your URL’s if you do have dynamic pages?

Officially the only reason your should do this is if you have more than 2 parameters in your url. This can be a massive job and the most important thing to note is that if your pages have 1 or 2 parameters and have been spidered by Google it is best to let them be. You could simply damage their rankings if you go re-writing your site pages.

However possibly for a brand new site that has dynamic URL’s their is still a case to say it can be worth re-writing your URL’s to be search engine friendly. This is because although they are now spidered and indexed they still may be treated in slightly different ways to static pages.

In July last year Matt Cutt’s released the following video

In it he says “We do treat static and dynamic pages in a similar way for ranking. Pagerank flows to dynamic URL’s in the same way they flow to static URL’s. So, if you’ve got New York Times, linking to a dynamic URL, you will still get the Pagerank benefit, and will still flow the Pagerank Benefit. There are other Search Engine’s who in the past have said they will go one-level deep from static URL’s, so we are not going to crawl from dynamic URL’s, but we will crawl from static URL’s to a dynamic URL. The short answer is, Pagerank still flows between static and dynamic. The example you (the person asking the question) give actually has 5 parameters, and one of them is a Product ID with like 2725. You definitely CAN use too many parameters, so I would opt for 2 or 3 at the most, if you have any choice whatsoever. Try to avoid long numbers, because we can think that those are session ID’s. Any extra parameters that you can get rid of are always a good idea and remember that Google is not the only Search Engine out there, so if you have the ability, to basically say I’m going to use a little bit of mod_rewrite and make it look like a static URL, that can often be a very good way to tackle the problem. So, experiment! If you don’t see any URL’s that have the same structure, or the same number of parameters as you are thinking about doing; it’s probably better if you can cut back on the number of parameters or shorten them somehow or try to use mod_rewrite”

They key thing i have picked up on from this quote is the word “similar”. This to me suggests that Google does treat dynamic pages in a slightly different way to static ones. There is also a school of thought that suggests Google trusts Dynamic pages less than static ones even though larger sites inevitably rely more and more on dynamic pages and URL’s. In the quote above Matt Cutts is almost suggesting hiding the fact that your pages are dynamic from Google to see if this improves rankings.

Ultimately search engines will get better and better at spidering dynamic sites, however there are still quite a few grey areas which may mean you might want to opt for a safe option if launching a new site and re-write URL’s to appear static.