var isSafari3 = false; 

//window.devicePixelRatio &&  window.getMatchedCSSRules is only implemented by Safari 3 now.
if( window.devicePixelRatio &&  window.getMatchedCSSRules ){
	//you need 	put html {list-style-image:none;} in yout Safari 3 only stylesheet first
	//we detect whether if it's Safari 3 by checking if it read some Safari 3 only styles 
    isSafari3  =  !!window.getMatchedCSSRules(document.documentElement,'');
}