If you would like to edit the color, font, or style of any elements, you would edit this css files
- [YourMagentoDir] / skin / frontend / default / [YOUR THEME] / css /
How to locate style definition for the element
Please use Google Chrome development toolbar or FF Firebug. Right-click on any page element and select Inspect element.
How to detect the line in the css file
You will find the line
It is possible to remove position: absolute; or change bottom: **px. This moves "Add to cart" button up.