Underscores are now word separators
Google soon to recognise underscores in URLs
Matt Cutts recently announced that Google would soon treat underscores in URLs as word separators by Google. Historically this was not possible so a URL like site.com/film_review .html the Googlebot couldn’t ‘see’ the words film or review. Instead it read film_review as one word, so not a lot of sense there!
Soon however, Google will be able to separate out the two words and read these as ‘film review’ as they can for URLs like site.com/film-review.html.
So should you change anything? Probably not. Using hyphens looks better for users and works fine and this is deemed as being ‘best practice’. We would guess that these changes have made to help blogs, such as Typepad, that use underscores as well as regular sites.
For those who do use underscores you may well see an increase in taffic as your URLs are brought into line with others as Google may give a little extra weighting to the newley recognised keywords in URLs, although some may disagree on that point. Lets wait and see!