Search Optimized Filenames: Dashes Versus Underscores
I've had many discussions with clients regarding the use of dashes versus underscores as word separators. For example: "web_design_company.htm" VS. "web-design-company.htm". The question is whether or not the search engines interpret them the same way. As it turns out, dashes may be the best way to go, at least from an SEO perspective. Stumbled upon a relevant post from Google's Matt Cutts, here's his take on it: http://www.mattcutts.com/blog/dashes-vs-underscores/