The cookie that tracks your offer purchase has to be intact in order to communcate back to the site which will in turn grant you credit for the offer. here is my checklist, others may not agree with all of them, but its what I use at least. Peter also has his guide HERE and Shaggz has a super awesome one HERE.
Open Internet Explorer/Firefox
Go to Tools>Internet Options>Privacy>Accept ALL cookies and turn off popup blocker
Turn off spyware/virus/firewall
Clear cookies and Temp internet files in browser
Open browser back up and sign in or register at the freebie site.
Hold cntrl to temporarily turn off any popup blockers, Click the offer, check the open cookies folder to make sure cookies appear
Wait for credit.
:" border="0" alt="1272062755-useremo.gif" />
True, better be careful than sorry. Some people seem to be trustworthy but in reality is not.
Nice post. Helps a lot