Making webpages look good cross-platform can be nightmare. I usually try and fix it with a little help from PHP and include a separate CSS file depending on which browser is used. This helps, me at least , to organize my stylesheets better. I make a version for each browser I wish to support and that does not comply with eachother and insert the following PHP code snippet:

if(strstr($HTTP_USER_AGENT, "Mozilla")){$user_agent = "Mozilla";}
if(strstr($HTTP_USER_AGENT, "Konqueror")){$user_agent = "Konqueror";}
if(strstr($HTTP_USER_AGENT, "IE")){$user_agent = "IE";}

and

echo("\n");

into the .php file. This way of course doesn't work if the user chooses to mask his/her browser as anotherone but that is more or less out of ones control. This also means that the CSS files have to be named like for instance "stylesheet_Mozilla".

Oh, and thanks sunsnapper for the tip about sizes. I was looking for that somewhere.