Naming your files

Each designer has their own way of thinking when it comes to naming files and documents.
Personally, I like to keep document names succinct, but obvious enough that I can find
them rapidly via a trawl of my hard drive. Certain conventions, however, are key: all file
names should avoid illegal characters (such as spaces), and it’s good to be consistent
throughout your site. I find that naming files in lowercase and replacing spaces with
hyphens—like-this-for-example.html—works well.

Web designers have historically used underscores in place of spaces, but that
causes problems with some search engines, some of which run-in keywords,
effectively considering the words within the file name as one string. This
doesn’t happen with hyphens.