$(document).ready(function(){
    $(".main").height("auto");
    if ( $(".main").height() < $(window).height() - $(".header").height() - $(".footer").height())
    {
        $(".main").height($(window).height() - $(".header").height() - $(".footer").height());
        $(".main > .center").height($(".main").height());
    }
});

$(window).resize(function(){
    $(".main").height("auto");
    if ( $(".main").height() < $(window).height() - $(".header").height() - $(".footer").height())
    {
        $(".main").height($(window).height() - $(".header").height() - $(".footer").height());
        $(".main > .center").height($(".main").height());
    }
});

$(window).scroll(function(){
    //$("div.main div.left_menu").animate({margin-top: window.pageYOffset}, 1500);
    var scrollY = 0;
	if( typeof( window.pageYOffset ) == 'number' ) {
		//Netscape compliant
		scrollY = window.pageYOffset;
	} else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) {
		//DOM compliant
		scrollY = document.body.scrollTop;
	} else if( document.documentElement && ( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) {
		//IE6 standards compliant mode
		scrollY = document.documentElement.scrollTop;
	}

    $("div.main div.left_menu").animate({ top: scrollY }, { duration: 2000, queue: false });
});