In between the <body> tags you'll just add a div with an id of "if_not_homepage" and the site will only read the contents of this div if not on the default.asp page. For example:
OR you could call a separate stylesheet completely from within this div (for example):
<link rel="stylesheet" href="/v/vspfiles/templates/YOUR_TEMPLATE/css/inner_style.css" />
If you place the stylesheet within the directory "/v/vspfiles/templates/YOUR_TEMPLATE/css/" you'll be able to edit the stylesheet from within the File Editor in the Volusion dashboard as well (like your other stylesheets).
Alternately, there is a div with an id of "if_homepage" that is read only if the user is on the default.asp (opposite of "if_not_homepage").
On a completely separate note, in your code above, you are missing either a class (.) or id (#) selector on 'content' in your CSS, so that may have something to do with it as well.