Quick Start or Fast Start is one adware which can be very annoying in any browser.Here are steps how to remove it :
Step 1 :
Go Tools/Add-ons and in Extensions remove Fast Start or Quick Start adware
Step 2 :
Now we need to remove chrome://quick_start/content/index.html from Firefox browser tab.
Write in Mozilla in search : about:config
Then type in search : browser.newtab.url and find this preference.
Change it to: about:newtab
Problem is solved.