Website Slowing Browser

Whenever I am using the forum Yahoo! Answers my PC runs extremely slow. In fact it happens whichever machine I use (Acer laptop, HP desktop or iPhone). Occasionally a message pops up saying a website is making my browser (Firefox) run slow, do I want to close the website or wait. What it does not do is tell me which website is the culprit. I have two questions. Is there a way I can find out which website is causing the problem? Is there anything I can do about it? With respect to my first question I believe it has to be Yahoo! Answers because it happens even when that is the only website I am on.

 

If you are not using extensions like AdBlockPlus and NoScript in Firefox, then many other (sometimes dozens) of websites run at the same time as they 'partners' of Yahoo. Use those extensions to block them so only Yahoo Answers site script runs.
https://addons.mozilla.org/en-GB/firefox/addon/noscript/
https://addons.mozilla.org/en-GB/firefox/addon/adblock-plus/?src=ss
uBlock Origin is an alternative to AdBlock Plus: https://addons.mozilla.org/en-GB/firefox/addon/ublock-origin/?src=ss