With stylish you can specify a domains using @-moz-document url-prefix(http://)
for example.
This applies to all URLs. Is there a way to specify which URLs you don't want the style to affect? This means you could have a global stylesheet that effects everything except specified URLs where there is another stylesheet you want to use.
This can get tricky but it can be done.
From the the Stylish documentation: "Applying styles to specific sites":
@-moz-document regexp('(?!http://www\.example\.com).*') {
/* CSS rules here.*/
}
Will activate for all URLs except those that start with http://www.example.com
.