HEAD/ GET requests?

[keyplyr]

Moved from Tracking and Logging [webmasterworld.com]

Every time I see double requests (once using HEAD, once using GET) for the same file, it's always from a MAC user, example:

XXX.116.189.154 - - [11/Dec/2003:00:27:07 -0800] "HEAD /file.type HTTP/1.0" 200 220 "-" "Mozilla/4.7 (Macintosh; I; PPC)" 
XXX.116.189.154 - - [11/Dec/2003:00:27:07 -0800] "GET /file.type HTTP/1.0" 200 220 "-" "Mozilla/4.7 (Macintosh; I; PPC)" 

Is this something MAC always does, or is this coincidence? Could this be related to downloading for offline access?

Thanks