'if compare http://msdn.microsoft.com/en-us/library/ms537512.aspx ! [if !IE] The NOT operator. This is placed immediately in front of the feature, operator, or subexpression to reverse the Boolean meaning of the expression. lt [if lt IE 5.5] The less-than operator. Returns true if the first argument is less than the second argument. lte [if lte IE 6] The less-than or equal operator. Returns true if the first argument is less than or equal to the second argument. gt [if gt IE 5] The greater-than operator. Returns true if the first argument is greater than the second argument. gte [if gte IE 7] The greater-than or equal operator. Returns true if the first argument is greater than or equal to the second argument. ( ) [if !(IE 7)] Subexpression operators. Used in conjunction with Boolean operators to create more complex expressions. & [if (gt IE 5)&(lt IE 7)] The AND operator. Returns true if all subexpressions evaluate to true | [if (IE 6)|(IE 7)] The OR operator. Returns true if any of the subexpressions evaluates to true. 'browser http://rafael.adm.br/css_browser_selector/ <?php $msie = strpos($_SERVER["HTTP_USER_AGENT"], 'MSIE') ? true : false; $firefox = strpos($_SERVER["HTTP_USER_AGENT"], 'Firefox') ? true : false; $safari = strpos($_SERVER["HTTP_USER_AGENT"], 'Safari') ? true : false; $chrome = strpos($_SERVER["HTTP_USER_AGENT"], 'Chrome') ? true : false; ?> <!--[if IE 8]> <p>Welcome to Internet Explorer 8.</p> <![endif]--> ie - Internet Explorer (All versions) ie8 - Internet Explorer 8.x ie7 - Internet Explorer 7.x ie6 - Internet Explorer 6.x ie5 - Internet Explorer 5.x gecko - Mozilla, Firefox (all versions), Camino ff2 - Firefox 2 ff3 - Firefox 3 ff3_5 - Firefox 3.5 ff3_6 - Firefox 3.6 new opera - Opera (All versions) opera8 - Opera 8.x opera9 - Opera 9.x opera10 - Opera 10.x konqueror - Konqueror webkit or safari - Safari, NetNewsWire, OmniWeb, Shiira, Google Chrome safari3 - Safari 3.x chrome - Google Chrome iron - SRWare Iron