SEO Advice

Its a well known fact that Google looks at URLs when determining keyphrase relevance to the web pages in your site. Always use hyphens and not underscores in your URLs. This includes files names and directories. The reason why is because Google disregards underscores (_) but interprets hyphens (-) as a space.

So if you had a web page all about search engine marketing, you would name the file like this:

search-engine-marketing.html

And not

search_engine_marketing.html

The latter example with the underscores is interpreted as searchenginemarketing whereas the example with the hyphens is seen as search engine marketing.