if(document.images) {
  portfolio_on = new Image;
  portfolio_on.src = '../img/portfolio_on.gif';
  portfolio_off = new Image;
  portfolio_off.src = '../img/portfolio_off.gif';
  
  referenzen_on = new Image;
  referenzen_on.src = '../img/referenzen_on.gif';
  referenzen_off = new Image;
  referenzen_off.src = '../img/referenzen_off.gif';
  
  derpalast_on = new Image;
  derpalast_on.src = '../img/derpalast_on.gif';
  derpalast_off = new Image;
  derpalast_off.src = '../img/derpalast_off.gif';
  
  presse_on = new Image;
  presse_on.src = '../img/presse_on.gif';
  presse_off = new Image;
  presse_off.src = '../img/presse_off.gif';
  
  neues_on = new Image;
  neues_on.src = '../img/neues_on.gif';
  neues_off = new Image;
  neues_off.src = '../img/neues_off.gif';
  
  kontakt_on = new Image;
  kontakt_on.src = '../img/kontakt_on.gif';
  kontakt_off = new Image;
  kontakt_off.src = '../img/kontakt_off.gif';
  
  impressum_on = new Image;
  impressum_on.src = '../img/impressum_on.gif';
  impressum_off = new Image;
  impressum_off.src = '../img/impressum_off.gif';
}

function imgAct(img_name)
{
  if(document.images) {
    img_on = eval(img_name + '_on.src');      
	  document.getElementById(img_name).src = img_on;
  }
}

function imgInact(img_name)
{
  if(document.images) {
    img_off = eval(img_name + '_off.src');          
    document.getElementById(img_name).src = img_off;
  }
}