var menu;
var menuY;
var categories;

function setMenu()
{
    menu = $('menu');
    menuY = menu.offsetTop; //221
    categories = $('categories');
}

window.onscroll = function()
{
    if(menu == null) setMenu();
    if( window.XMLHttpRequest ) {
        if (document.documentElement.scrollTop > menuY || self.pageYOffset > menuY) {
            menu.style.position = 'fixed';
            menu.style.top = '0';
            menu.style.width = '900px';
            categories.style.backgroundImage = 'url(http://27dv.com/wp-content/themes/Sharpfolio/images/minilogo.png)';
            categories.style.backgroundRepeat = 'no-repeat';
            categories.style.backgroundPosition = 'right';
        } else if (document.documentElement.scrollTop < menuY || self.pageYOffset < menuY) {
            menu.style.position = 'relative';
            categories.style.backgroundImage = 'none';
        }
    }
   
}