例
<style type="text/css">.parent { opacity:.5;}.parent div { opacity:1; /* I want this to override the ".5",but instead it combines */}</style><div class="parent"><div></div></div>
#my_element { /* ie6 fallback - no opacity */ background-color:rgb(255,255,255); /* rgba(red,green,blue,alpha); */ background-color:rgba(255,0.5);}
