I definitely saw an ad that was targeted specifically for me on a site
I visit frequently. There was simply no doubt because of the nature of
the ad. Until a week ago I had cookies and Flash enabled, and I was
using Firefox. Then I deleted all cookies and selected Firefox's
option to delete all cookies every time I exit Firefox. Also, I found
and eliminated the 2 sub-folders in "C:\Documents and Settings" where
the cookies from Flash and Macromedia are stored. I'm not stupid
either when it comes to computers, I'm almost certain I have no
viruses or spyware of any sort, I have an excellent firewall, and just
to be sure, after receiving this specific ad, I researched and
downloaded the Spybot software, ran it, and just as I expected, it
said I have no spyware or anything on my drive. I know that no spyware
detector is safe, but I'm not stupid when it comes to computers, and I
just don't think it has to do with that.

But despite erasing all my previous identifying marks, today, after
changing my IP address and deleting the sub-folders again, I visited
that website and they showed me the ad that was targeted specifically
at me. My question is, how did they do it? I have a theory of my own,
I think that since they have my previous browsing history when they
receive a hit from someone they haven't identified yet they rely on
their stored data to send an ad to the most likely person behind the
anonymous hit. Using my IP range, the time of day when I visited the
site, the browser version, and of course the website I visit, they
reduce the possibilities to 1 or 3 people from their database and then
their computer picks an ad that it would have selected for one of
those people if it had been him and sends it to the anonymous browser.

I have a good reason to believe I may be right. I changed my IP
address again, erased all cookies and Flash/Macromedia garbage, and
then logged on to the same site just 5 minutes later with Internet
Explorer, which I never used to visit this site. They gave me a non-
specific general ad. I did this trick another 3 or 4 times, switching
between Firefox and Internet Explorer, and every time I logged on with
Firefox they gave me the same very specific ad, and every time I
logged on with Internet Explorer they gave me a general non-specific
ad. That looks to me like they are trying to guess who I am based on
the bits and pieces of info they can gather from my browser's request.

What do you guys think?
Thanks for your help.
A concerned warrior... "tonight we browse in Hell !!!!!"