Managing a custom CSS is a nightmare, but making changes to it is even more so – especially if you need to make the same change in lots of places. My solution – applying T4 to CSS, thereby creating a Site.css style only as a byproduct of a Site.tt template:

<#@ output extension=".css" #> 
<#
  string fontFamily = "Calibri, Arial, Helvetica, Sans-Serif";
  int fontSize = 12; // px
#>
body, p, td, li, a, input { font-family: <#= fontFamily #>; }
body
{
  font-size: <#= fontSize #>px;
  background-color: Black;
  color: White;
}
h1, h2 { font-family: <#= fontFamily #>;
         font-weight: normal }


Another problem solved.