if (document.images) {
  navHome = new Image
  navHomeOver = new Image
  navRep = new Image
  navRepOver = new Image
  navBook = new Image
  navBookOver = new Image
  navCont = new Image
  navContOver = new Image

  navHome.src = 'imgs/nav_home.gif'
  navHomeOver.src = 'imgs/nav_home_over.gif'
  navRep.src = 'imgs/nav_rep.gif'  
  navRepOver.src = 'imgs/nav_rep_over.gif'
  navBook.src = 'imgs/nav_book.gif'
  navBookOver.src = 'imgs/nav_book_over.gif'
  navCont.src = 'imgs/nav_cont.gif'
  navContOver.src = 'imgs/nav_cont_over.gif'
}