jQuery opacity animation
jQuery's .animate() takes values from 0 to 1.
$(document.body).animate({opacity: 0}, 1000);$(document.body).animate({opacity: 1}, 1000);I'm sure that .animate() must call .parseFloat() (or something) on the values you're passing, which would make your 0% into 0 (which is correct), but your 100% into 100, which would be incorrect.
You can use functions or something like this:
$(document.body).animate({ opacity: 1/2 }, 1000);