A site's URL structure should be as simple as possible. Consider organizing your content so that URLs are constructed logically and in a manner that is most intelligible to humans (when possible, readable words rather than long ID numbers). For example, if you're searching for information about aviation, a URL like http://en.wikipedia.org/wiki/Aviation will help you decide whether to click that link. A URL like http://www.example.com/index.php?id_sezione=360&sid=3a5ebc944f41daa6f849f730f1, is much less appealing to users. Source Url: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=76329
URL structure is the link structure of your particular website with proper linking to the internal pages.
i agree with MR Right, the good url is contain your keyword. if your keyword "blog personal", so the good url is : yoursite.com/blog-personal/
URL structure always follow in static if have dynamic page then you can make clean url so that will be search engine friendly, use keywords in URL with hyphen separator don't use space in url
URL structure should be http://www.yourwebsitename.com/{4-5 words using keywords} I think this would be best..
A site's URL structure should be as simple as possible. The URL structure is the another important feature for the search engine optimization. Try to make the URL static and descriptive as to be search engine as well as user friendly.