Blue-Bye-You CSS FF prob

This is what I get for thinking the world runs on that pitiful IE browser. I’ve worked out a lot of the problems I had with modifying the Blue-Bye-You theme to my own liking at http://thesilverblue.com/wp — it displays perfectly in IE, but in FF and Netscape the Calendar jumps over to the right, as well as the “flashback” section. Then things correct themselves, until you go down to recent comments and trackbacks. Any idea as to how to correct this? (I’ll admit I’m a sloppy coder, as I don’t fully understand CSS).

Any help would be greatly appreciated. (I’ll also say that the header image shifts in Opera, but I don’t know how many people are using Opera… so I’m not too concerned about that as I am with the FF issues)