Originally Posted by mayavipoly
i'm a new user dont know the codes to enter. please help
First, someone asked what version of Ubuntu. Is it 7, or 9??? Again, 7 is VERY old, so if this is a new install, get the latest version of Ubuntu, and load it.
Next, you say your "monitor" says that. How about telling us what KIND of monitor? What kind of video card? We're not going to guess. And not sure what you mean by "codes to enter". There are no magic 'codes'...either your monitor supports the resolution you chose, or it doesn't. YOU need to look at the specs on your monitor, to see what it supports.
You can boot into 'rescue' mode with your install media, and a quick Google search turns up many answers to changing your screen resolution...did you bother to try to look this up?
That link has links to other how-tos, and you can even search on this very site for info on how to do it.