Underscores or Hyphens
in File Names
Which is best ?
A very clear answer to this question - Hyphens every time.
Google continues to the be leading search engine in the world - and many aspects of the way Google operates have been copied by other search engines.
Google was written by computer Geeks - and computer Geeks and programmers often use underscores. For this reason, Google recognises an underscore, i.e. _ as a character.
So, if you create a page file name, for instance, of search_engine.htm, Google will recognise from that the word search_engine - but that is something most people will not type !
If the same page has the file name search-engine.htm Google will recognise from this the words search and engine as well as the phrase search engine.
So, hyphens all the time and, perhaps more importantly, never underscores in file names. Now, the latter part of that you may have to tell your web programmer !
As to the argument about whether it is best to run words together, e.g. searchengine, or have them hyphenated - well, that is an argument for another time !