Can't open video on youtube and can't browse?but other apps are ok.why?pls help.

I Checked the wifi connection its ok and accessible.but so weird when i use safari search something it just gonna stop and sooner there is a pop-up : the server stop reponding. And it also happened on my youtube.i can open the app(it means the internet is ok) but when i click a video and an error pop-up again: error loading captions! Whats wrong with my iphone!....