CSS browser specific targets selector, rules, statements and pseudo-classes

css-browser-specific.md

Opera:

Docs for > Opera 9.5

doesnotexist:-o-prefocus, .example {
    /*The following will apply rules to 'example' class in Opera only.*/
}

Firefox:

Docs document (at-rule)

• url(), which matches an exact URL
• url-prefix(), which matches if the document URL starts with the value provided
• domain(), which matches if the document URL is on the domain provided (or a subdomain of it)
• regexp(), which matches if the document URL is matched by the regular expression provided. The expression must match the entire URL.

    @-moz-document url-prefix() {
        
      .selector{
        /*Rules applyed to 'selector' class only in Firefox*/
      }
    }

The @document rule is an at-rule that restricts the style rules contained within it based on the URL of the document. It is designed primarily for user style sheets. A @document rule can specify one or more matching functions. If any of the functions apply to a URL, the rule will take effect on that URL.