var menu_last='';
var menu_active='';

function switch_menu(el)
{
    var ext = '';
    
    if(el=='')
    {
	el=menu_active;
    }
    
    if(el!='')
    {
	ext = '_'+el;
    }
    
    var imgl = document.getElementById('menuimg'+menu_last);
    imgl.style.display="none";
    
    var img = document.getElementById('menuimg'+ext);    
    img.style.display="block";
    
    menu_last=ext;
}

function menu_open(el)
{
    var iframe = document.getElementById('contentframe');
    var jetzt = new Date();
    
    iframe.src=el+".html?hash=" + jetzt.getTime();
    document.location.hash=el;
    
    menu_set_active(el);
    
    return true;
}

function menu_set_active(el)
{
    var ext='';
    if(el!='')
    {
	ext='_'+el;
    }
    var img = document.getElementById('menuimg'+ext);
    
    if(img)
    {
	menu_active=el;
        switch_menu(el);
    }
}

function menu_load()
{
    if(document.location.hash!='')
    {
	var seite = document.location.hash.split('#')[1];
	var testing = /^[a-zA-Z0-9]*$/;
	if(testing.test(seite))
	{
	    var iframe = document.getElementById('contentframe');
	    iframe.src=seite+'.html';
	    
	    menu_set_active(seite);
	}
    }
}