some.css

#container{ 
max-width: 700px;
min-height: 700px;
}
* html #container{ 
width: expression( document.body.clientWidth > 699 ? "700px" : "auto" );/* ie6 */
height: expression( document.body.clientWidth < 701 ? "700px" : "auto" );/* ie6*/
}


.clearfix:before, .clearfix:after {
  content:"";
  display:table;
}
.clearfix:after{
  clear:both;
}
.clearfix{
  *zoom:1;/*ie6,7*/
}


.transparent_class { 
  -ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=50)"; /* ie8  */
  filter:alpha(opacity=50);    /* ie5-7  */
  -moz-opacity:0.5;    /* old mozilla browser like netscape  */
  -khtml-opacity: 0.5;    /* for really really old safari */ 
  opacity: 0.5;    /* css standard, currently it works in most modern browsers like firefox,  */
}


#box{
  color:red; /* 所有浏览器都支持 */
  color:red !important;/* 除IE6外 */
  _color:red; /* IE6支持 */
  *color:red; /* IE6、IE7支持 */
  +color:red;/*IE7支持*/
  *+color:red; /* IE7支持 */
  color:red\9; /* IE6、IE7、IE8、IE9支持 */
  color:red\0; /* IE8、IE9支持 */
  color:red\9\0;/*IE9支持*/
}