/*it doesn't work in ie*/
html body center div#usrbar{
background:transparent url(http://hiphotos.baidu.com/zhouqicf/pic/item/3e8de890ac4effa6a877a462.jpg) no-repeat scroll center top !important;
color:#000000 !important;
filter:none !important;
height:30px !important;
padding:0 !important;
width:150px !important;
}
html body center div#usrbar:hover{
background-position:center 30px !important;
height:60px !important;
width:auto !important;
}
html body center div#usrbar nobr{
display:none !important;
height:30px !important;
line-height:30px !important;
background-color:#4f4f4f !important;
color:#4f4f4f !important;
}
html body center div#usrbar:hover nobr{display:block !important;}
div#nav_extra,div#nav_extra_app{top:5px !important;}
html body center div#usrbar a,html body center div#usrbar a:link,html body center div#usrbar a:visited{color:#f2f2f2 !important;text-decoration:none !important;font-size:14px;}
html body center div#usrbar a:hover{text-decoration:underline !important;}
body #nav_extra a,body #nav_extra a:visited{color:#333 !important;}
body #nav_extra a:hover{color:#fff !important;background-color:#333 !important;}
#usrbar img.down-arrow{border-color:#4f4f4f;}
#nav_extra .body, #nav_extra_app div.body{border-color:#333;}

http://hi.baidu.com/zhouqicf/blog/item/06479bdb0969af6fd1164e4f.html

onmouseover:show the userbox
onmouseout:hidden the userbox
自定义百度空间的用户栏，当鼠标移上去的时候展开，鼠标离开时隐藏。

A style For Baidu Hi Userbox

CSS