If you don't know what a HOST file is you should, in case please see these links:
http://winhelp2002.mvps.org/hosts.htm (main file)
http://hosts-file.net/ (addon for real pest)
http://hostsfile.mine.nu/ (unneeded/unwanted ads)
Don't stick your head in the sand and hope these sites won't send your PC junk while surfing. Always use CCleaner when done using internet to remove web trash.
If you're confused????? then download Hostman (sorry I'd didn't name it) and it will download install and keep your HOST file updated.
You may add sites to the HOST file by editing the text (notepad) file i.e. "127.0.0.1 www.donotsendmeyourads.com" and then save. Example you installed a program from company www.junkware.com the the host edit would be "127.0.0.1 www.junkware.com" without quotes to keep them from sending ads about other programs you're not interested in.
Doing computers since 1965: Geek1945