[html] How to set page content to the middle of screen?

If you want to center the content horizontally and vertically, but don't know in prior how high your page will be, you have to you use JavaScript.

HTML:

<body>
    <div id="content">...</div>
</body>

CSS:

#content {
    max-width: 1000px;
    margin: auto;
    left: 1%;
    right: 1%;
    position: absolute;
}

JavaScript (using jQuery):

$(function() {
    $(window).on('resize', function resize()  {
        $(window).off('resize', resize);
        setTimeout(function () {
            var content = $('#content');
            var top = (window.innerHeight - content.height()) / 2;
            content.css('top', Math.max(0, top) + 'px');
            $(window).on('resize', resize);
        }, 50);
    }).resize();
});

Centered horizontally and vertically

Demo: http://jsfiddle.net/nBzcb/