Fixing Code Difference in FF and IE

Hello guys,

I am still having problems with how my site looks in IE. It looks OK in FF. Where could i be getting it wrong? Thanks guys, please come throough...

The code is as below,

<html>

<head>

<title>Testing CSS</title>

#container{width:80%; height:100%;}

#header{width:100%; height:25%; background-image:url(image.jpg); background-color:blue; border-bottom:double thin blue;}

#menu{width:20%; height:100%; background-color:pink; border-right:double thin blue; border-left:double thin blue; float:left;}

#center{width:75%; height:100%; background-color:white; float:left;}

#right{width:4%; height:100%; background-color:yellow; float:right; border-right:double thin blue;}

#footer{width:100%; height:5%; background-color:blue; clear:both;}

.menu a{display:block; background-color:blue; text-decoration:none;}

.menu a:hover{display:block; background-color:white; text-decoration:none;}

.menu a:visited{display:block; text-decoration:underline;}

body{background-color:gray;}

h2{text-align:right;}

span{background-color:#3BB9FF;}

</style>

</head>

<body>

</DIV>

<p>Welcome!

</DIV>

</DIV>

</center>

</body>

</html>