In the world of optimizing your page URLs for SEO, there comes the discussion of using dashes (or hyphens) versus underscores.

For example...

1. search-engine-optimization.htm

2. search_engine_optimization.htm

The answer is to ALWAYS use dashes, (example #1 above).

This is because Google recognizes the dash as a separator, but doesn't do so for underscores. Hence in the first example, it actually sees three separate words, but in the second example, it sees it as one long string of characters.

The end result is that the first example will optimize much better with Google.

You can watch a video of Matt Cutts explain this specific question...

http://www.youtube.com/GoogleWebmasterHelp#play/uploads/81/Q3SFVfDIS5k  ✓