var myrules = {
    'div#show img' : function(el){
        el.onmouseover = function(){
            var filename = this.src
            filename = filename.replace("a.jpg","b.jpg")
            this.src = filename;
        }
        
        el.onmouseout = function(){
            var filename = this.src
            filename = filename.replace("b.jpg","a.jpg")
            this.src = filename;
        }
    },
    'div#impressum a' : function(el){
        el.onclick = function(){
            return toggle_impressum()
        }
    }
};

Behaviour.register(myrules);

function toggle_impressum(){
    // after loading the site, the visibility i get is an empty string though the div is hidden
    // what the heck?
    if(document.getElementById("impressum_hidden").style.visibility == "")
    {
        document.getElementById("impressum_hidden").style.visibility = "hidden"
    }
    
    if(document.getElementById("impressum_hidden").style.visibility == "hidden")
    {
        document.getElementById("impressum_hidden").style.visibility = "visible"
    }
    else
    {
        document.getElementById("impressum_hidden").style.visibility = "hidden"
    }
    return false
}