Dashes or Underscores to separate keywords in url/path?

topics: google ranking , google optimization , ranking

Directory/page names play a role in Google ranking. Nowadays It's a fact a very few webmasters ignore.
Therefore, it is easy to find Url's like:

http://www.yourdomaincool.com/pizza_with_salami/
salami_flavour_for_pizza.html

or

http://www.your-domain-cool.com/pizza-with-salami/salami-flavour-for-pizza.html

(notice that I have written "play a role" and NOT "play a BIG role": an effective google optimization is a complicated job, it cannot be reduced to pagenames. For a very detailed, affordable, effective Google ranking report, check out Battlefield 1.0 suite or Battlefield 1.0 the-report-only)

Assuming that the following formats:

http://www.yourdomaincool.com/pizzawithsalami/salamiflavourforpizza.html

and

http://www.yourdomaincool.com/pizza%20with%20salami
/salami%20flavour%20for%20pizza.html

are uneffective at all, the question is: which method (dashes or underscores) is more effective?

The answer is (many will be surprised): DASHES work great, while underscores are uneffective, as Google does NOT recognize them as word separators.

WHAAAAAT???????????

Yes, that's true. And we're going to prove that Google considers pizza_with_salami as a single. unique, word (and since Google does not make any stemming of the words...this is useless)

1. Let's search pizza-with-salami (dashes)

http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=pizza-with-salami&btnG=Google+Search

results: 72

2. Let's search pizza_with_salami (underscores)

http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=pizza_with_salami&btnG=Google+Search

No matches (oops)

3. Let's search "pizza with salami" (with quotes)

http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=%22pizza++with+salami%22&btnG=Google+Search

70 results (first results' page is almost the same of pizza-with-salami query)...