cross-browser right sidebar

I'm trying to create a sidebar of fixed width. The following code
works in IE7 but not FF2. What's the best approach to do this in both
of these browsers?

<html>
<head>
<style>
#right {
float: right;
background-color: Silver;
height: 300px;
width: 100px;
margin-left: 50;
}

#left-1 {
background-color: Lime;
height: 100px;
margin-right: 30;
}

#left-2 {
background-color: Yellow;
height: 100px;
margin-right: 160;
}
</style>
</head>
<body>
<div id="right">blah<br />blah<br />blah<br /></div>
<div id="left-1">blah</div>
<div id="left-2">blah</div>
</body>
</html>

TIA,
David
.

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