IPhone safari won't open some web pages?

I have the iPhone 5 and all of a sudden I cannot get certain websites to open that I frequently use. I had someone else try to access them on their phone and they opened fine. I get the message that safari stopped responding because it cannot find the server. Can anyone help please?

Perhaps your parents enabled restrictions on your phone?

Perhaps you have reached your data limit and those pages are too rich to be loaded with slower access?