How do I delete my entire internet history?

[Yangggdf Dfsdf]

I've deleted my browsing history in Firefox, however when I type in boxes on certain websites it has a scroll down of past text I have typed. How do I remove this?

 

[Aaron-Four]

download ccleaner from here:

CCleaner - PC Optimization and Cleaning - Free Download

 

[I do not know]

Try ATFcleaner link:
ATF-Cleaner.exe - www.atribune.org

It'll only take a few seconds to download and run it. It'll clear your entire computer history in under 20 secs.