When typing name of websites in location bar in Firefox, by default it will show a list of similar named websites from history as well as from the bookmarks list. To prevent these sites from showing up :

1. Click on Edit > Preferences in Linux based Firefox (or Tools > Options in Windows based Firefox).

2. Select the Privacy tab and under the Location bar section, change the option “When using the location bar, suggest History and Bookmarks” to “Nothing”.

All done. From now on, websites from history as well as those which are bookmarked will not show up when a website name is typed in the Firefox location bar for surfing.

Cheers.