Consistently, e-cop, your ethics-cop, is gonna show you an example:
Look a screenshot taken from twitpic.com and take your time to locate the crap bullshit ad:

Politely, e-cop warned tweetpic, in its ethic-driven motto, posted a complain about this important issue, in the company technical service page, with sucking answer, dig it.
Fortunatelly, e-cop is here to give the solution.
save the following script in a local file:
<config version="1.0">
<page name="TwitPic - Ad" url="http://*twitpic.com/*" enabled="true">
<xpath comment="">/html/body/center/div[1]/div[1]/div[2]/div[2]/div[7]</xpath>
</page>
</config>
If you use Firefox (you must upgrade inmediately in case you use the unpronounceable explorer), install the RIP addon from:
the RIP firefox addon
after restarting firefox, go to tools->options->rip options and press the "import rip..." button, load then the script you saved previously.
Job done!, visit again the twitpage or any other, and W00t!!, No sucking ads!!, anymore!!

One more time, e-cop, your ethic angel, saved innocent people from falling under the crappy advertiser networks.
god save the queen