Apple iPhone

I would like to get an I phone but I go into the at&t store to play with them and if I am in the browser all of a sudden, it will go back to the home screen. this is not the first time, and this is not the only phone I have played with the iphone at a few different stores, and the same thing happens? I asked the sales person, only on had any kind of answer, that the broweser cashe was full, so i went into the settings and cleares all the cookies and everything i could. But it did not seem to work. Nice phone, But if it crashes al the time, I do not know?
Any body have any input?