margin-collapse-026

Margin collapsing - in-flow block-level margins with an element 'height' of 'auto' and 'min-height' of zero

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Flags
ahem, image
Assertion
An element's margins are adjoining and can collapse if the 'min-height' is zero, if it has no top or bottom borders and no top or bottom padding, if it has a 'height' of zero or 'auto', if it has no line boxes and if all of its in-flow children's margins are adjoining.

Source

 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
 2 <html>
 3     <head>
 4         <title>CSS Test: Margin collapsing - in-flow block-level margins with an element 'height' of 'auto' and 'min-height' of zero</title>
 5         <link rel="author" title="Microsoft" href="http://www.microsoft.com/">
 6         <link rel="help" href="http://www.w3.org/TR/CSS21/box.html#collapsing-margins">
 7         <meta name="flags" content="ahem image">
 8         <meta name="assert" content="An element's margins are adjoining and can collapse if the 'min-height' is zero, if it has no top or bottom borders and no top or bottom padding, if it has a 'height' of zero or 'auto', if it has no line boxes and if all of its in-flow children's margins are adjoining.">
 9         <style type="text/css">
10             div
11             {
12                 font: 20px/1em Ahem;
13                 width: 5em;
14             }
15             #div1
16             {
17                 background: url('support/margin-collapse-2em-space.png');
18                 height: 4em;
19             }
20             #div3
21             {
22                 background: red;
23                 height: auto;
24                 min-height: 0;
25             }
26             #div2, #div5
27             {
28                 background: green;
29                 height: 1em;
30             }
31             #div3, #div4
32             {
33                 margin-bottom: 2em;
34                 margin-top: 2em;
35             }
36         </style>
37     </head>
38     <body>
39         <p>Test passes if there is no red visible on the page.</p>
40         <div id="div1">
41             <div id="div2"></div>
42             <div id="div3">
43                 <div id="div4"></div>
44             </div>
45             <div id="div5"></div>
46         </div>
47     </body>
48 </html>