The 'core CSS' I refer to is '/qa-theme/Default/qa-styles.css'. There are a couple of ways to merge in a custom style sheet.
1. Add another LINK tag to the header template. Already there is the main sheet:
HTML Code:
<link rel="stylesheet" type="text/css" href="./qa-theme/Default/qa-styles.css?1.4.1">
<!-- which can be accompanied by, -->
<link rel="stylesheet" type="text/css" href="./qa-theme/Default/qa-custom.css">
Of course, your custom file would need to be where we say it is, in the "./qa-theme/Default/" folder.
One could just as easily create a "/qa-theme/Custom/" folder, and put your custom code in there for easy organization and audit. Remember, the idea of custom modules is to keep us away from the original code. The principle is that we always want to be able to back out of what we've done. With a custom folder, we can turn off our additional code with the flip of a switch.
The link tag has to be after the main CSS link in order to have higher specificity. The facebook link tag should be last (after yours) to prevent any conflicts..
2. Load your custom CSS from the link in the header template, and have that style sheet import the main sheet:
HTML Code:
<link rel="stylesheet" type="text/css" href="./qa-theme/Default/qa-custom.css">
And the CSS:
Code:
qa-custom.css
/* first line in the code */
@import "./qa-theme/Default/qa-styles.css?1.4.1";
/* custom CSS below */
The thing to keep in mind is that if you upgrade your theme to a newer version than the one referenced, you will have to edit this CSS file, not the header template.
As to the code not being in your style sheet, it wouldn't be there--it's inline somewhere in a body module template. A quick search of your local folder (Desktop Search or if you have it search site using Dreamweaver) for the text in question should turn up the php module(s) that contain(s) it.