I agree, netscape is **** . My "Programming for the Web" teacher (who is nice but rather naive) said today 90% of people use IE 5. I doubt this statistic, but its true that IE is far better.
But thats irrelevent. If he chooses to make his site for both IE and NS (without browser-specific pages and such), let him. But it will be hard. The first step, like TN said, is to run your code through a HTML validator. IE has many nice features, but it allows very sloppy code, a mixed blessing.
If you're still having problems, copy the code into a .txt file and post it for download. Embedding code into these threads is a pain, plese don't do it.