eBay does not serve pop-up ads. Or maybe they do. I don't know, I've never seen one, because I keep my computer clean and take preventative measures.
The first two are addons for the Firefox browser, which must be installed first. AdBlock Plus does what it's name says, it blocks ads. NoScript prevents scripts from running on sites you do not approve of, such as the site that may have done a drive-by install of a pop-up program.
The last is nothing but a text file. When obtained from a source that has frequent updates, the computer is then prevented from ever connecting to most known adware/malware sites, such as those that serve pop-up ads. I recommend http://winhelp2002.mvps.org/hosts.htm .
ADBLOCK PLUS!! Google it. It's free with Safari, Firefox, SeaMonkey, Chrome, Opera, etc. It will also block ads on YouTube videos and other websites. I haven't seen an ad in YEARS!