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

Answer 1

Make the CSS content this way...

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

#container {
    height: auto;
    width: 90%;
    margin: 0 auto;
    background-color: #FFF;
    padding: 10px;
}

A working example is here: http://jsfiddle.net/golchha21/mjT7t/