Background color is not displayed when setting div height to auto! What for?

Question

The background color # of the container is not displayed when I set its height to auto. But it shows when I set it to a fixed height, like 1000 pixels. I tried overflow: auto, but that didn't work. How can i fix this? I want the #container to expand vertically according to its contents, and I want to show its background color. Any idea would be much appreciated!

Here is the HTML:

<div id="container">
    <div id="main">
        <div id="div1">text text text text text text text text text text text texttexttext text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text</div>
        <div id="div2">text text text text text text text text text text text texttexttext</div>
        <div class="clear"></div>
    </div><!--end of main-->
</div><!--end of container-->

Here is the CSS:

#container {
    background-color: rgb(255, 102, 204);
    height: auto;
    width: 1200px;
    position: absolute;
}
#container #main {
    background-color: rgb(204, 51, 0);
    height: auto;
    width: 900px;
    position: absolute;
    overflow: auto;
}
#container #main #div1 {
    background-color: rgb(0, 204, 255);
    float: left;
    width: 300px;
    padding: 5px;
    height: auto;
    margin: 20px;
}
#container #main #div2 {
    background-color: rgb(0, 153, 153);
    height: auto;
    width: 400px;
    float: left;
    margin: 10px;
}
.clear {
    clear: both;
}

Answer 1

, , . .

, jsfiddle :)

!!! . lazychio, , .

Answer 2

, #main div position:absolute;. , position:absolute; position:fixed; , , , .

, w3schools

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