window.scrollMaxY can be set via that property in IE and older versions of Firefox, but when trying in FF3 it says "Cannot set this property as it only has a getter". What is my alternative? EDIT: The reason why I'm asking is that I'm fixing some very horrible JS written by someone else, it has a function to keep a div centered on the page while scrolling, and has this line: // Fixes Firefox incrementing page height while scrolling window.scrollMaxY = scrollMaxY Obviously this doesn't work, but the main issue is that when the page is scrolled, it grows in length.