How do I stop End-less floating Div in JavaScript?

I am building a new theme for my blog and I need to do it before 1st Jan. Its almost com开发者_运维知识库plete but I am encountering a problem:

See this post for example

The last 2 Widgets i.e., FEATURED POSTS and RECENT POSTS in sidebar are set to float (positioned absolute, floating widgets become fixed when user scrolls to it) so that they are always visible when a user scrolls down. But how do i stop floating after reaching the footer? Any help would be really appreciated.

From what I can see you use some javascript that changes the box to position:fixed once your scrollposition is equal to the top of the box. What you need is some sort of check to see if the bottom of the box is less than a given length from the bottom of page. Say for instance is length from bottom is less or equal to 100px you can turn it back to position:absolute and set bottom to 100px. Then of course add a check to see set it back to fixed if the user scrolls up again. Just work a little with the script you got there and you'll have a solution, don't have the ability to test a script from the comp I'm at atm so can't help you with that.