Very Simple steps to clear or delete history in browsers. sometimes, it may differ from OS to OS. but you can follow the below ground rules.
Firefox 3.7 & Above :
Click on Menus : History>Show All History>Under Library Click on the period you want to delete. > Right click on item and choose delete.
Chrome Browser :
Click on wrench icon>choose History item>Click on Edit item on right top>Clear all browsing data.
Click on Internet Options from Menu>Click on delete under Browsing History Panel.
Happy Surfing and cleaning