if (document.images) {
    welcoff = new Image
    welcon = new Image
    homeoff = new Image
    homeon = new Image   
    aboutoff = new Image
    abouton = new Image  
    abacon = new Image   
    abacoff = new Image  
    conton = new Image   
    contoff = new Image
    usinon = new Image    
    usinoff = new Image
    kimpon = new Image    
    kimpoff = new Image   
    toyon = new Image    
    toyoff = new Image           
    topson = new Image   
    topsoff = new Image 
    downoff = new Image
    downon = new Image  
    scisoff = new Image
    scison = new Image    
    searon = new Image   
    searoff = new Image 
    browon = new Image   
    browoff = new Image 
   
 
    welcoff.src = "images/button_welcome2.gif"
    welcon.src = "images/button_welcome2_over.gif"
    homeoff.src = "images/button_home2.gif"
    homeon.src = "images/button_home2_over.gif"   
    aboutoff.src = "images/button_about2.gif"
    abouton.src = "images/button_about2_over.gif" 
    abacoff.src = "images/button_about_act2.gif"       
    abacon.src = "images/button_about_act2_over.gif"
    contoff.src = "images/button_contact2.gif"
    conton.src = "images/button_contact2_over.gif"  
    usinoff.src = "images/button_reading2.gif"
    usinon.src = "images/button_reading2_over.gif"
    kimpoff.src = "images/button_partners2.gif"
    kimpon.src = "images/button_partners2_over.gif"
    toyoff.src = "images/button_toy.gif"
    toyon.src = "images/button_toy_over.gif"
    topson.src = "images/button_topsell_over.jpg"  
    topsoff.src = "images/button_topsell.jpg" 
    downoff.src = "images/button_download.jpg"
    downon.src = "images/button_download_over.jpg"   
    scisoff.src = "images/button_science2.jpg"
    scison.src = "images/button_science2_over.jpg"    
    searon.src = "images/button_search_over.jpg"  
    searoff.src = "images/button_search.jpg" 
    browon.src = "images/button_browse_over.jpg"  
    browoff.src = "images/button_browse.jpg" 
  
 }
else{
    welcoff = ""
    welcon = ""
    document.WELCL = ""
    homeoff = ""
    homeon = ""
    document.HOMEL = ""    
    aboutoff = ""
    abouton = ""
    document.ABOUTL = ""
    abacoff = ""
    abacon = ""
    document.ABACL = ""    
    contoff = ""
    conton = ""
    document.CONTL = "" 
    topsoff = ""
    topson = ""
    document.TOPSL = ""
    downoff = ""
    downon = ""
    document.DOWNL = ""
    scisoff = ""
    scison = ""
    document.SCISL = ""                
    searoff = ""
    searon = ""
    document.SEARL = ""   
    browoff = ""
    browon = ""
    document.BROWL = ""
    kimpoff = ""
    kimpon = ""
    document.KIMPL = ""
    toyoff = ""
    toyon = ""
    document.TOYL = ""

}