if (document.images) {
img1on = new Image();           
img1on.src = "media/profile_en_on.gif";  
img2on = new Image(); 
img2on.src = "media/collaboration_en_on.gif";  
img5on = new Image();           
img5on.src = "media/iform_en_on.gif";  

img1off = new Image();          
img1off.src = "media/profile_en.gif";  
img2off = new Image();
img2off.src = "media/collaboration_en.gif";  
img5off = new Image();          
img5off.src = "media/iform_en.gif";  
}

function imgOn(imgName)
{
        if (document.images)
        {
            document[imgName].src = eval(imgName + "on.src");
        }
}

function imgOff(imgName)
{
        if (document.images)
        {
            document[imgName].src = eval(imgName + "off.src");
        }
}