I would like to get some opinions on what is the best structure for URLs for SEO. It is my understanding that the best structure to use is hyphens to separate words, for example: http://www.cit.com/main/financial-solutions/corporate-finance/ as opposed to no space such as: http://www.handiramp.com/yardramp.htm or underscore such as http://www.handiramp.com/non-skid_safety_tread.htm What is your opinion?
As delimiters hypens and dashes are the best options to use, neither one gets any more value over the other. You can see this by Wikipedia as example using underscores and being in the top of many different search results. Whichever you choose I suggest you use them with all URLs and don't mix them up. However, dashes are used more often because visitors can actually remember those URLs easier. But, when it comes to search engines it makes no difference to them which delimiter you use.
I agree with ssandecki. Hypens and dashes are the best options to use in structuring a quality URL, and also looks nicer since it separates a two or more different word in a URL that makes the URL more readable.
I pick cit.com/main/financial-solutions/corporate-finance.I've seen the other used but not as often so go with the first.