I am designing a web site using Firefox, but when I check the page using IE, it does not look good. Also, different screen sizes produce different results. How can I standardize the code?

Browser: Firefox

OS: Mac

A web page will automatically adjust itself to fit the screen size available unless you explicitly force it to do otherwise.

Remember that with larger screens people may not have the browser window maximised so the visitor's screen resolution is not always a good guide.

If you don't want a fluid layout then the best option is to create a fixed width, centred, design.

I thought I did design a centered, fixed page. With smaller screens stuff gets wrapped. There doesn't seem to be enough room for the whole page, so it wraps. How can I allow for this? Can I check viewers screen size and change it on the fly?

I'm having trouble finding information on screen/browser compatibility.

Browser: Firefox

OS: Mac

The fact that browsers can often adapt pages to fit whatever is available is something you could see as an advantage, not a problem. You may want to look at this page

But having a fixed width page is OK, as long as you accept that this means empty space on high resolutions. I think you should get along just well with a fixed width of 640. (No, I know 640x480 isn't most peoples choice of resolution any more, but it is what most printers can handle)