How to increase/decrease current margin at a number by jquery?

Question

Given an element with unknown margin-left, how to increase its margin-left at a number say 100px?

For example:

assuming the original margin-left is 100px

Answer 1

A quick/terse way to do this:

$('#IDHere').animate({marginLeft: '+=100px'}, 0);

Here's a quick example of this. The 0 makes this happen in a single frame, if you actually want to animate it, change the 0 to the number of milliseconds you want, like this.