Check seems to work for Firefox and Chrome (tested my blog using latest versions); IE - well it's IE...
However, in Opera 12.02 a line is shown:
Warning: preg_match_all() [function.preg-match-all]: Compilation failed: unrecognized character after (?< at offset 3 in ../wp-content/plugins/advanced-browser-check/output.php on line 87
Despite the settings, this may make ABC to show up mistakenly?