#公告层
{
float: left; 
width: 21em; 
height:10em;   
padding: 5px; 
border: 1px dotted #3399FF; 

overflow: hidden
}

#最新消息层
{
float: left; 
width: 21em; 
height:10em; 
padding: 5px; 
border: 1px dotted #3399FF;
overflow: hidden
}
#搜索层
{
padding: 5px; 
border: 1px dotted #3399FF; 
float: left; 
width: 16em;
height:10em; 
overflow: hidden;
}
#数学概率层
{
float: left; width: 21em; padding: 5px; border: 1px dotted #3399FF;
height:11em; 
overflow: hidden;
}
#算法层
{
float: left; width: 21em; padding: 5px; border: 1px solid #F9C282;
height:11em; 
overflow: hidden;
}
#生活数学趣味数学层
{
float: left; width: 16em; padding: 5px; border: 1px solid #00CC00;
height:11em; 
overflow: hidden;
}
.平行层高度类
{
height:11em; 
overflow: hidden;
}