$(document).ready(function() {

    var viewportwidth;
    var viewportheight;

    // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight

    if (typeof window.innerWidth != 'undefined')
    {
    viewportwidth = window.innerWidth,
    viewportheight = window.innerHeight
    }

    // IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)

    else if (typeof document.documentElement != 'undefined'
    && typeof document.documentElement.clientWidth !=
    'undefined' && document.documentElement.clientWidth != 0)
    {
    viewportwidth = document.documentElement.clientWidth,
    viewportheight = document.documentElement.clientHeight
    }

    // older versions of IE

    else
    {
    viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
    viewportheight = document.getElementsByTagName('body')[0].clientHeight
    }
    if (viewportheight < 800) {
	 $('#header #logo a').css('display', 'none');
	 }
 });