If its a free host then, the problem is from their clientpanel setting but if its a paid host and they have told u its working wella on their pc then....
_Drop me ur site url and ur host let me take a look at it?
_Are u using xhtml codes, jsp or php scripts?
before that i advice u open ur admin option settings and take a critical look at every change u made recently.. No rushing jeje ur problem focal point will be gotten and thrashed out. Dont forget to drop me the url and host
0818391167 is the number