Por que navegadores diferentes processam o mesmo HTML de maneira diferente?

Question

Aug 20, 2010, 02:42 PM

html rendering jquery mozilla internet-explorer-8

Por que navegadores diferentes processam o mesmo HTML de maneira diferente?

Esta é uma página html:

<html>
<head>
<title>
Frame Set
</title>
<script type="text/javascript" src="jquery-1.4.2.min.js"></script>
<link rel="stylesheet" href="frame.css" type="text/css" media="screen" />

<script language="JavaScript" type="text/javascript">
$(document).ready(function() {
    var winSize = $(window).width();
    var margin = (winSize-1000)/2;;
    $('#main').css({'margin-left':margin,'margin-right':margin});  
    }
)
$(function() {
  $(".frame").each(function() {
     var width = ($(this).find('.h').width()), 
         height = $(this).find('.l').height(),
         pad = $(this).find('.h').position().left,
         actWidth = width + 10,
         nHeight = height - (height * 2),
         rLeftMargin = actWidth - 1,
         bWidth = actWidth;

    $(this).find('.r').css({'margin-top':nHeight, 'margin-left':rLeftMargin, 'height':height});
    $(this).find('.h').css({'height':25});
    $(this).find('.b').css({'width':bWidth, 'margin-top':0});
  });
});
</script>
</head>
<body>
<div id="main" align="center" style="width:1000px; height:100%; text-align:left;">
    <div id="inner1" style="width:100%; height:20%; float:top; margin-bottom: 20px;">
        <div id="inner11">
            <div class="frame">
                <div class="h" style="width:100%">Header</div>
                <div class="l" style="height:93%"></div>
                <div class="r"></div>
                <div class="b"></div>
            </div>
        </div>
    </div>
    <div id="inner2" style="width:100%; height:60%;">
        <div id="inner21" style="width:69%; float:left; margin-left: 1px; margin-right: 1px;">
            <div class="frame">
                <div class="h" style="width:100%">Left Frame</div>
                <div class="l" style="height:93%"></div>
                <div class="r"></div>
                <div class="b"></div>
            </div>
        </div>
        <div id="inner22" style="width:29%; float:right; margin-left: 1px; margin-right: 1px;">
            <div class="frame">
                <div class="h" style="width:100%">Right Frame</div>
                <div class="l" style="height:93%"></div>
                <div class="r"></div>
                <div class="b"></div>
            </div>
        </div>
    </div>
    <div id="inner3" style="width:100%; height:20%; float:bottom; margin: 2px 2px 2px 2px;">
        <div id="inner23">
            <div class="frame">
                <div class="h" style="width:100%">Footer</div>
                <div class="l" style="height:93%"></div>
                <div class="r"></div>
                <div class="b"></div>
            </div>
        </div>
    </div>
</div>
</body>
</html>

Esta é a saída do Mozilla:

Esta é a saída do IE8:

Qual é o problema ?