Our LESS should not use psuedo-selectors that are not supported in IE 8 (using it in a jQuery selector is fine). Common ones that are not supported are :not and :empty.
The obvious exception is things like:
where it intentionally uses the construct so IE 8 drops the rule.
There is one sub-bug about this already, but I'm not planning to make a separate one for each other case. Let's just fix them.