Importance of URL Structure

[RobertChapman]

We are trying to restructure our onpage SEO and want to make sure we have our URLs correct.  The problem is we did the URLs incorrectly in the first place and the ones we currently have are several years olds.

We have some URLs such as: http://www.firebrandtraining.co.uk/courses/management/prince2.asp and 
http://www.firebrandtraining.co.uk/courses/cisco/ccna_2007.asp which are not ideal but user experience aside does it make sense for us to change the URLs and use 301 redirects to the new ones or is the damage done to our natural rankings simply not worth making the change?

I have read different articles saying different things, some say that URL structure has little weight (if any weight at all) on rankings while other people seem to say it is quite important.

In addition we have heard that changing the URLs with a 301 redirect will cause a large drop in ranking which will take months to recover from and contrarily that 301s are now considered "ok" by Google and we shouldn't see too much change at all in our rankings.

Any advice would be much appreciated.

[DougRoberts]

I don't think the URLs are an absolute disaster.

Before making any changes like this you need to understand the potential risks and clearly define what it is you are trying to achieve.

Look at how many links/linking domains each of your pages have. It's these deep links that are both the most valuable to the pages and also the ones most at risk.

How many pages do you have on your site, how much organic search traffic do you already attract? Where are you currently ranking for your chosen keywords?

If you've got lots of deep inbound links and the URLs aren't causing a significant problem then I don't think I'd take the risk. Even if it all goes well, you'll lost some "link juice" in the redirects.

What will be the return on investment of your time re-structuring your URLs and 301 redirecting all the content to the new pages vs the potential loss of rankings/traffic?

Hope this helps.