false premise, nice idea Rated 2 out of 5 stars
"You will need not to restart firefox after changing your hosts file... c:\windows\system32\drivers\etc\hosts"
Only if you have opted to embrace the masochism of the DNS Client service in XP (and newer / not better)
The XP varient of this client is far too clingly, requiring far too many "tweaks". Either use a third party caching tool, your own LAN resolver, or find a public resolved faster than whatever OVERLOADED (oversold) resolvers employed by your ISP. This is NOT an endorsement for OpenDNS or other 'free' resolver that wickedly does not return NXDOMAIN.