In case you didn't know or needed actual mathmatical proof. There were only 7 days in 2004 in which Internet Explorer was safe from some kind of security exploit or hack. This means 98% of the time in 2004 your somputer could have been compromised by known flaw in IE. Firefox was only unsafe for 56 days of 2004.
You can read the entire report here.
Or you could just take my word for it and Download Firefox.
What about Opera? Ever use it? I found it a bit too complicated and awkward for my taste the one time I tried it.
The report metions Opera too. It was slightly safer than Firefox but this is probably becasue no one has gone to a lot of effort to exploit it.