by Jim » Mon Aug 27, 2012 2:59 pm
It depends on the template you have assigned what css file will be used, (or if the css is included on the page). So view the html source of the shopping cart and see what .css files are included. In Firefox when viewing the html source you can click on the link to the css file and it will open in the browser window. (After viewing the css file you need to right click on the page and select Back to get back to the original html source)
If you find the file that has the names of the styles that are assigned to the elements displayed by the [-- SC_CART --] tag then that is the file you will need to edit. (Note that frequently there is a separate .css file for each section of the shopping cart template, Shopping cart, Checkout screen, Confirmation Screen, Thank you screen , so you will need to modify all of the css files referenced by those screens also).
If you go to http://www.shopsite.com/templates/cookbook/builtintemplates.shtml and click on the theme that you are using you can get a list of the files used by the theme. That might help so you don't have to view all the html and search for the .css files that are used.
You might also be able to define or redefine the classes for the styles by putting them in the "Text at top of xx screen" (where xx is Shopping cart, checkout, confirmation, thank you) on Commerce Setup > Order System .