Your browser history on your PS3? No... Nothing serious will get deleted. When you use your browser again it just won't remember what you visited last time along with any saved log-in info.
So if I look up something I want to keep secret, and I push the erase cookies, history, and ache, will it erase it completely from my PS3? Will it be impossible for someone to stumble across it or even find it intentionally? I wanna make sure it cannot be found.
Don't worry, no one in your household will know what you search for at odd hours of the night if you erase the cookies/cache/history of your browser.
Lots of people like My Little Pony. It's really okay.