Linux Mail Server Setup and Howto Guide

Hi All
I need your help on this problem
I have blocked the downloading of the files with file formats as listed
below;It works okey when you try to download by clicking on the link BUT
when you right-click on a link and select the option save link as, it
allows downloads;Does anyone know how to deal with this?

# Access Denied Section
# ============================================== #
# Only allow cachemgr access from localhost
# Only allow purge requests from localhost
acl blockfiles urlpath_regex -i "/etc/squid3/blocks.files.acl"
acl workhours1 time MTWHF 08:00-12:59
acl BlockedSites dstdomain .facebook.com .myspace.com .twitter.com
.warez.com .quepasa.com .yahoo.com .mail.google.com
acl workhours2 time MTWHF 14:00-16:59
http_access deny workhours1 BlockedSites
http_access deny BlockedSites workhours2 blockfiles
#Content of blocks.files.acl
\.[Ee][Xx][Ee]$
\.[Aa][Vv][Ii]$
\.[Mm][Pp][Gg]$
\.[Mm][Pp][Ee][Gg]$
\.[Mm][Pp]3$
\.[Mm][Pp]4$

Regards
John