margin-collapse-024

Margin collapsing - in-flow block-level margin adjoining child's margin

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Flags
ahem, image
Assertion
When an in-flow block-level element (#div3) is adjoining its in-flow block-level child's top margin and the child has no top border, no top padding or no clearance applied to it, then such top margins collapse.

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 margin adjoining child's margin</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="When an in-flow block-level element (#div3) is adjoining its in-flow block-level child's top margin and the child has no top border, no top padding or no clearance applied to it, then such top margins collapse.">
 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             #div2, #div4
21             {
22                 background: green;
23                 height: 1em;
24             }
25             #div3
26             {
27                 background: red;
28             }
29             #div3, #div4
30             {
31                 margin-top: 2em;
32             }
33         </style>
34     </head>
35     <body>
36         <p>Test passes if there is no red visible on the page.</p>
37         <div id="div1">
38             <div id="div2"></div>
39             <div id="div3">
40                 <div id="div4"></div>
41             </div>
42         </div>
43     </body>
44 </html>