Menu déroulant vers le haut en css

#column_bottom { 
 position:relative; 
        width:1000px; 
 margin:0 auto; 
        padding:17px 0 0 0; 
 font-size:0.8em; 
 text-align:center; 
} 
#cssmenu{ height:37px; display:block; padding:0; margin:20px auto;  border:1px solid; border-radius:5px; }  
#cssmenu > ul {list-style:inside none; padding:0; margin:0;}  
#cssmenu > ul > li {list-style:inside none; padding:0; margin:0; float:left; display:block; position:relative;}  
#cssmenu > ul > li > a{ outline:none; display:block; position:relative; padding:12px 20px; font:bold 13px/100% Arial, Helvetica, sans-serif; text-align:center; text-decoration:none; text-shadow:1px 1px 0 rgba(0,0,0, 0.4); }  
#cssmenu > ul > li:first-child > a{border-radius:5px 0 0 5px;}  
#cssmenu > ul > li > a:after{ content:''; position:absolute; border-right:1px solid; top:-1px; bottom:-1px; right:-2px; z-index:99; }  
#cssmenu ul li.has-sub:hover > a:after{top:0; bottom:0;}  
#cssmenu > ul > li.has-sub > a:before{ content:''; position:absolute; top:18px; right:6px; border:5px solid transparent; border-top:5px solid #fff; }  
#cssmenu > ul > li.has-sub:hover > a:before{top:19px;}  
#cssmenu ul li.has-sub:hover > a{ background:#3f3f3f; border-color:#3f3f3f; padding-bottom:13px; padding-top:13px; top:-1px; z-index:999; }  
#cssmenu ul li.has-sub:hover > ul, #cssmenu ul li.has-sub:hover > div{display:block;}  
#cssmenu ul li.has-sub > a:hover{background:#3f3f3f; border-color:#3f3f3f;}  
#cssmenu ul li > ul, #cssmenu ul li > div{ display:none; width:auto; position:absolute; top:38px; padding:10px 0; background:#3f3f3f; border-radius:0 0 5px 5px; z-index:999; }  
#cssmenu ul li > ul{width:200px;}  
#cssmenu ul li > ul li{display:block; list-style:inside none; padding:0; margin:0; position:relative;}  
#cssmenu ul li > ul li a{ outline:none; display:block; position:relative; margin:0; padding:8px 20px; font:10pt Arial, Helvetica, sans-serif; color:#fff; text-decoration:none; text-shadow:1px 1px 0 rgba(0,0,0, 0.5); }  

#cssmenu, #cssmenu > ul > li > ul > li a:hover{ background:#3e698c; background:-moz-linear-gradient(top,  #3e698c 0%, #30576e 100%); background:-webkit-gradient(linear, left top, left bottom, color-stop(0%,#3e698c), color-stop(100%,#30576e)); background:-webkit-linear-gradient(top,  #3e698c 0%,#30576e 100%); background:-o-linear-gradient(top, #3e698c 0%,#30576e 100%); background:-ms-linear-gradient(top, #3e698c 0%,#30576e 100%); background:linear-gradient(top,  #3e698c 0%,#30576e 100%); filter:progid:DXImageTransform.Microsoft.gradient( startColorstr='#3e698c', endColorstr='#30576e',GradientType=0 ); }  
#cssmenu{border-color:#1b313d;}  
#cssmenu > ul > li > a{border-right:1px solid #1b313d; color:#fff;}  
#cssmenu > ul > li > a:after{border-color:#6696bd;}  
#cssmenu > ul > li > a:hover{background:#436f93;} 

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<div id='cssmenu'> 
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