You can clone with
HTTPS or Subversion.
This is not helpful:
Selector syntax error
Especially when using CSS generated from less, when the link in the right hand column goes to the raw html source, without the generated CSS embedded in it
Similar non-helpful error message:
Even just adding Unknow at-rule: @doesnotexist with the above non-context would help in finding the rule (or in filtering it)
Unknow at-rule: @doesnotexist