How to use HTML5 in IE 7?

I was wondering whether there is a way to make html5 code visible in Internet Explorer 7 or less.

For example

<div id="container"> 
    <header id="header"> 
        something 
    </header>
</div>

In Internet Explorer 7 the header is not shown at all.

I found a workaround here, a IE HTML5 enabling script, which creates the html5 elements with javascript. But what happens is that the <header> tag looks not at all as it does in other browsers.

So my question is, is it too early to use HTML5 yet or how can I make it cross-browser working?