How can I center a div within another div? [duplicate]

Answer 1

Try to get the position:relative; in your #container. Add an exact width to #container:

#main_content {
    top: 160px;
    left: 160px;
    width: 800px;
    min-height: 500px;
    height: auto;
    background-color: #2185C5;
    position: relative;
}

#container {
    width: 600px;
    height: auto;
    margin: auto;
    padding: 10px;
}

Working demo

Answer 2

It would work giving the #container div width:80% (any width less than the main content and have given in %, so that it manages well from both left and right) and giving margin:0px auto; or margin:0 auto; (both work fine).

Answer 3

Maybe you want as this: Demo

HTML

<div id="main_content">
    <div id="container">vertical aligned text<br />some more text here
    </div>
</div>

CSS

#main_content {
    width: 500px;
    height: 500px;
    background: #2185C5;
    display: table-cell;
    text-align: center;
    vertical-align: middle;
}

#container{
    width: auto;
    height: auto;
    background: white;
    display: inline-block;
    padding: 10px;
}

How?

In a table cell, vertical align with middle will set to vertically centered to the element and text-align: center; works as horizontal alignment to the element.

Noticed why is #container is in inline-block because this is in the condition of the row.