As explained by Matt Cutts in the Google Webmaster Help YouTube video, dashes in the URLs are used to separate two words whereas underscores combine both words into one. In SEO terms this means that when using a dash to separate words in your URL, Google will index all of these terms individually. When using an underscore Google will only index your combination of words as one.
Question: Should you change your existing pages URL layout to dashes?
Answer: No, if you make changes to your pages current URL layout you will lose your search rankings. If you are just starting out your website or are adding new pages to your site it is recommended that you then use dashes in your URL.
If you have questions about your website’s current URL layout please comment below or use our live chat feature.