You can now customize the one page checkout form using custom CSS.
You can download the base checkout CSS file at the following URL:
Launch your template editor, and edit the "Styles / checkout.css" file with any modifications to the base CSS file.
If you have the one-page checkout enabled and would like to use custom CSS, you will just need to ensure that the first line of the CSS file contains:
/* Checkout Version: 2.0 | DO NOT REMOVE */
If the one page checkout is enabled for your account, and the first line does not read as above, we will automatically use the default CSS.