html弹出层，背景半透明，用于提示或确认

html-pop-layout

   <div class="back" style="position: fixed !important; background-position: center center;
        position: absolute; top: 0; left: 0; height: 100%; width: 100%; z-index: 999;
        background: #000 no-repeat center center; opacity: 0.8; filter: alpha(opacity=80);
        font-size: 14px; line-height: 20px; display: none;">
    </div>
 <div  class="pop_winwrap"  style="text-align: center; position: absolute;
        top: 30%; left: 30%; margin: 20px 0 20px 0px; padding: 3px 3px 3px 10px; z-index: 1000; background:
        opacity: 1.0; filter: alpha(opacity=100);  display:none; ">
		<img class='' id="" src="images/img.png" style="cursor: pointer;" />
	</div>