Stating " Select the encoding that makes your document readable"

How do I get this message to stop and have docs I'm trying to open from my
corporate web site open properly. I have a similiar issue with PDF files
with a meesage that reads " Adobe Acrobat could not open file XXX becasue
either it is not supported or is corrupted."" Problem is both these open fine
on my other computer 4 feet away so I don't think it s the web site.

Any sugestions??