Instructions
Go to the "Network" column of your PS3's main menu.
Select "Internet Browser."
Press the "Triangle" button to open the browser options menu.
Select "History" from the menu. The PS3 should display a list of all the websites it has visited.
Press "Triangle" again to access the history options menu.
Select the "Delete all" option and choose "Yes" when asked if you would like to delete your browsing history. The PS3 then deletes the log.