Superfish dropdown goes behind when published to server on IE

Its fine when I run it on Visual Studio but then it goes b开发者_运维知识库ehind if deployed to web server on IE. It works perfectly with Mozilla.

I found that the technique with IE was to supersede via its z-index and making the div at position:relative. See code example below.

Given this HTML.

<div id="header">
    <ul class="sf-menu"></ul>
    <div id="content"></div>
</div>

And, the CSS..

#header{z-index:2;position:relative;
}
#content{z-index:1;position:relative;
}

Then the superfish dropdown in IE should now always be on top of content.