non-compatible

Yesterday I wondered, is it really that difficult to make a website compatible with other browsers (other than IE)?

I do not know much about how to make them compatible with non-IE browsers; but I do know that it is annoying that some websites can't be seen with FireFox or Safari. The results tend to be a website that appears all messed up, fonts weird and links unavailable.

I hear the government tends to make their sites IE only...is there a reason for that? Isn't that like not having handicapped access to a public building?