function preloadImages(){
    left_nav_1 = new Image();
    left_nav_1.src = "gfx/icon-box-15-on.gif";
    left_nav_2 = new Image();
    left_nav_2.src = "gfx/icon-box-16-on.gif";
    left_nav_3 = new Image();
    left_nav_3.src = "gfx/icon-box-17-on.gif";
    left_nav_4 = new Image();
    left_nav_4.src = "gfx/icon-box-18-on.gif";
    left_nav_5 = new Image();
    left_nav_5.src = "gfx/icon-box-19-on.gif";
    left_nav_6 = new Image();
    left_nav_6.src = "gfx/icon-box-20-on.gif";
    left_nav_7 = new Image();
    left_nav_7.src = "gfx/icon-box-21-on.gif";
    left_nav_8 = new Image();
    left_nav_8.src = "gfx/icon-box-22-on.gif";
    teaser_link = new Image();
    teaser_link.src = "gfx/teaser_link.gif";
    teaser_link_hover = new Image();
    teaser_link_hover.src = "gfx/teaser_link_hover.gif";
}

function switchClass(id){

    if(document.getElementById(id).className == 'left_text_hidden'){

        document.getElementById(id).className = 'left_text_visible';

    }
    else{
        document.getElementById(id).className = 'left_text_hidden';
    }

}