html css picture
I want to make two pictures overlap and the top picture is transparent. How to do it? Beginner. Please give me some advice! !
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><style type="text/css">#logo{background:url(https://developer.cdn.mozilla.net/media/img/mdn-logo-sm.png)no-repeat center;width:62px;height:71px;} #logo img{filter:alpha(opacity=50); -moz-opacity:0.5; opacity:0.5;}</style></head><body><div id="logo"> <img src="https://mozorg.cdn.mozilla.net/media/img/firefox/new/header-firefox.png?2013-06" /></div></body></html>