function adjust_nav_position(){
    var scroll = $(window).scrollTop();
    var css = { 'position': 'inherit', 'top': '' };
    if(logo_top - scroll <= 40){
        css = { 'position': 'fixed', 'top': 40 };
    }
    $('#logo_wrap').css(css);
}

var logo_top = 0;

$(function(){
    logo_top = $('#logo_wrap').offset().top;
    $(window).scroll(function(){
        adjust_nav_position();
    });

    $("<img src='/images/logo_264_hover.png' />");

    var logo_image = $('#logo_image');
    logo_image.hover(function(){
        logo_image.attr('src', '/images/logo_264_hover.png');
    },function(){
        logo_image.attr('src', '/images/logo_264.png');
    });
});