if (document.images)
          {
            arcon= new Image(150,25);
            arcon.src="images/button_archivOver.gif";  
            arcoff= new Image(150,25);
            arcoff.src="images/button_archiv.gif";  
            
            curon= new Image(150,25);
            curon.src="images/button_currentOver.gif";  
            curoff= new Image(150,25);
            curoff.src="images/button_current.gif";  
            
            cou1on= new Image(200,35);
            cou1on.src="images/button_coursesOver.gif";  
            cou2on= new Image(150,90);
            cou2on.src="images/studyOver.jpg";

            cou1off= new Image(200,35);
            cou1off.src="images/button_courses.gif";
            cou2off= new Image(150,90);
            cou2off.src="images/study.jpg";
            
            par1on= new Image(200,35);
            par1on.src="images/button_partsOver.gif";  
            par2on= new Image(150,90);
            par2on.src="images/chemlabOver.jpg";

            par1off= new Image(200,35);
            par1off.src="images/button_parts.gif";
            par2off= new Image(150,90);
            par2off.src="images/chemlab.jpg";    
            
            con1on= new Image(200,35);
            con1on.src="images/button_contactOver.gif";  
            con2on= new Image(150,90);
            con2on.src="images/teachrOver.jpg";

            con1off= new Image(200,35);
            con1off.src="images/button_contact.gif";
            con2off= new Image(150,90);
            con2off.src="images/teachr.jpg";    
            
            lin1on= new Image(200,35);
            lin1on.src="images/button_linksOver.gif";  
            lin2on= new Image(150,90);
            lin2on.src="images/mainstOver.jpg";

            lin1off= new Image(200,35);
            lin1off.src="images/button_links.gif";
            lin2off= new Image(150,90);
            lin2off.src="images/mainst.jpg";            
          }

function lightup(imgName,imgName2)
        {
          if (document.images)
           {
             imgOn=eval(imgName + "on.src");
             document[imgName].src= imgOn;
             imgOn2=eval(imgName2 + "on.src");
             document[imgName2].src= imgOn2;
           }
        }

function turnoff(imgName,imgName2)
        {
          if (document.images)
           {
             imgOff=eval(imgName + "off.src");
             document[imgName].src= imgOff;
             imgOff2=eval(imgName2 + "off.src");
             document[imgName2].src= imgOff2;
           }
        }