Hello all, I'm sure this is not a super mega cool post, but well, I thought it may be good to share it.

Most of us web developers are used to using underscores when programming, and we're also getting used to using them in URLs. There's often asked if it's better to use dashes or underscores when writing URL addresses, and the answer everytime is the same: avoid using underscores on your URLs.

It's fairly simple, underscores are used in programming languages for very strict name matching such as _MAXINT. When using underscore in search engines they will always try to match the exact name, so if you're using underscores on your URL, you will appear sometimes only if somebody searches for CRAZY_CHICKS which most likely will never happen. By using dashes, a search such as "CRAZY CHICKS" will always produce good results if your URL's address is using dashes.

Hope it helps a bit.

mate,
if you use _ in ur url search engine bots will attach the two key words like

1)Windows-xp
here you get results for windows and xp

2) Windows_xp
here google bot understands like user is searching for windows xp
it ignores "_" and attach two words!

hope you got it
Thank you