redirection to a blocked url within my h

When I am reading my mail form Techrep. or Other Tech Mag. I try to get to another link within this mail but I am dircted to a blocked page.specially happen when the link starts with www.clickthru….
using XP Pro ,Norton 2002 antivirus and internet security .No virus on my system .
Please What s happenig ..Advise !
Thanks
Boukadhaba Ahmed