hello, unfortunately the search on our side will become broader the more search words you enter (which is rather unintuitive). you might want to try a google search instead: https://www.google.com/search?q=site%3Asupport.mozilla.org+prevent+video+autoplay

to answer your question directly - you might want to set the flash plugin to always ask in the firefox menu ≡ > addons > plugins...

Searching for something more specific like autoplay and checking Firefox under Relevant to: can give you more relevant results.

https://support.mozilla.org/en-US/search?esab=a&w=2&a=1&product=firefox&created=0&created_date=&updated=0&updated_date=&sortby=1&asked_by=&answered_by=&num_voted=0&num_votes=&q_tags=&q=autoplay

Most search engines will take the search string, and give you a listing of anything that matches any part of the string. I had started doing my searches by not having spaces between the words. This seams to get better results. <search.for.this>

By the way, try searching here;

Flash block {web link} Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on it