if (document.images) {
   back = new Image
   logo = new Image
   menu_logo_contact = new Image
   menu_logo_brochure= new Image
   menu_logo_news = new Image

   menu_logo_contact_on = new Image
   menu_logo_brochure_on = new Image
   menu_logo_news_on = new Image

   back.src="images/back.gif"
   logo.src="images/logo.gif"
   menu_logo_contact.src = "images/menu_top_text_contact.gif"
   menu_logo_brochure.src = "images/menu_top_text_brochure.gif"
   menu_logo_news.src = "images/menu_top_text_news.gif"

   menu_logo_contact_on.src = "images/menu_top_text_contact_on.gif"
   menu_logo_brochure_on.src = "images/menu_top_text_brochure_on.gif"
   menu_logo_news_on.src = "images/menu_top_text_news_on.gif"

}

function imageOver(imageName) {
        if (document.images) {
            document[imageName].src = eval(imageName + "_on.src");  
                          }
}
     
     function imageOff(imageName) {
        if (document.images) {
            document[imageName].src = eval(imageName + ".src");                        
                    }
}