In my recent seo research I now realize Google recognizes hyphens as dividers in image names, urls, and body content and ignores underscores. The underscore is not considered a divider (separator) by Google. So use hyphens not underscores in order for the search engines to recognize your keywords. Also keep your urls under 30 characters as it may be problematic for search engines to crawl and index them.

For more info on dashes vs underscores, check out Matt Cutts blog at http://www.mattcutts.com/blog/dashes-vs-underscores/

Many people ask me, what exactly is SEO? SEO is the abbreviation for search engine optimization. SEO consists of many techniques, that you apply to your website to help influence the search engines to not only rank your site with a higher ranking, but more importantly to rank the keywords you have carefully chosen that are relevant to your site, to list higher in the search engine listings. The bottom line here is to drive more visitors or traffic to your website, in order to increase your potential long-term customer base and profits. Read more »