How to make `margin: top;` based on browser height?
<p>The title pretty much says it all. I want the CSS <code>margin: top;</code> on my HTML <code>main_content</code> element to be relative to (a percentage of) the browser window (so that the <code>main_content</code> always stays on the bottom of the browser window. How can I accomplish this?</p>

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<p>I've tried this and it doesn't work. (the <code>body {height:100vh}</code> doesn't seem to make <code>body</code> any height as the <code>main_content</code> doesn't stick to the bottom as it should.</p>

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<pre class="snippet-code-css lang-css prettyprint-override"><code>body {height:100vh}
#main_content {position:absolute; width:100%; display:block; left:0; bottom:0; text-align:center; padding:20px;}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;Extra Infomation &lt;/div&gt;
&lt;div id="main_content"&gt;
&lt;p&gt;here you can learn about me and my adventures&lt;/p&gt;
&lt;/div&gt;</code></pre>
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<p>(Don't try this right now) If you go to my <a href="http://www.jeffarries.com" rel="nofollow">website</a>, you will see the "learn about me and my adventures" heading, that, along with the "recent activity", and other stuff below that, that is the section I want at the bottom of the browser window, preferably with the "learn about me and my adventures" part just sticking out from the bottom of the page.</p>