if (document.images) {
     button1a = new Image
     button1b = new Image
     button2a = new Image
     button2b = new Image
     button3a = new Image
     button3b = new Image
     button4a = new Image
     button4b = new Image
     button5a = new Image
     button5b = new Image
     button6a = new Image
     button6b = new Image
     button7a = new Image
     button7b = new Image
     button8a = new Image
     button8b = new Image

     button1a.src = 'img/menu01a.gif'
     button1b.src = 'img/menu01b.gif'
     button2a.src = 'img/menu02a.gif'
     button2b.src = 'img/menu02b.gif'
     button3a.src = 'img/menu03a.gif'
     button3b.src = 'img/menu03b.gif'
     button4a.src = 'img/menu04a.gif'
     button4b.src = 'img/menu04b.gif'
     button5a.src = 'img/menu05a.gif'
     button5b.src = 'img/menu05b.gif'
     button6a.src = 'img/menu06a.gif'
     button6b.src = 'img/menu06b.gif'
     button7a.src = 'img/menu07a.gif'
     button7b.src = 'img/menu07b.gif'
     button8a.src = 'img/menu08a.gif'
     button8b.src = 'img/menu08b.gif'
 }