没等移到二级菜单就消失了_html/css_WEB-ITnose

想实现二级菜单，
在ＣＳＳ中有；
#templatemo_left_link
{
margin-top:0px;
margin-left:25px;
line-height:33px;
font-family:Verdana, Arial, Helvetica, sans-serif;
font-size:12px;
font-weight:bold;
color:#ffffff;
}


#templatemo_left_link ul
{
width:70px;
list-style:none;
line-height:33px;
margin:0;
padding:0;
}

#templatemo_left_link ul li
{
position:relative;

display:block;
}

#templatemo_left_link ul li ul
{
display:none;
position:absolute;
width:70px;
float:left;
margin:0;
padding:0;
left:68px;
top:0px;
text-align:left;
list-style-type:none;
border:1px solid rgb(170,170,170);
background-color:rgb(238,238,238);
line-height:28px;
z-index:100;

}

#templatemo_left_link ul li ul li
{
float:left;
margin:0;
padding:0;
width:68px;
text-align:left;
border-bottom:1px solid rgb(204,204,204);
border-top:1px solid rgb(255,255,255);
}

在ＨＴＭＬ中有：