Practical solution to center vertically and horizontally in HTML that works in FF, IE6 and IE7

Question

What can be a practical solution to center vertically and horizontally content in HTML that works in Firefox, IE6 and IE7?

Some details:

• I am looking for solution for the entire page.

• You need to specify only width of the element to be centered. Height of the element is not known in design time.

• When minimizing window, scrolling should appear only when all white space is gone. In other words, width of screen should be represented as:

"leftSpace width=(screenWidth-widthOfCenteredElement)/2"+
"centeredElement width=widthOfCenteredElement"+
"rightSpace width=(screenWidth-widthOfCenteredElement)/2"

And the same for the height:

"topSpace height=(screenHeight-heightOfCenteredElement)/2"+
"centeredElement height=heightOfCenteredElement"+
"bottomSpace height=(screenWidth-heightOfCenteredElement)/2"

• By practical I mean that use of tables is OK. I intend to use this layout mostly for special pages like login. So CSS purity is not so important here, while following standards is desirable for future compatibility.

Answer 1

From http://www.webmonkey.com/codelibrary/Center_a_DIV

#horizon        
    {
    text-align: center;
    position: absolute;
    top: 50%;
    left: 0px;
    width: 100%;
    height: 1px;
    overflow: visible;
    display: block
    }

#content    
    {
    width: 250px;
    height: 70px;
    margin-left: -125px;
    position: absolute;
    top: -35px;
    left: 50%;
    visibility: visible
    }

<div id="horizon">
   <div id="content">
      <p>This text is<br><emphasis>DEAD CENTRE</emphasis ><br>and stays there!</p>
   </div><!-- closes content-->
</div><!-- closes horizon-->