var imagenumber = 11 ;
var randomnumber = Math.random() ;
var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1 ;
images = new Array
images[1] = "images/opendays/001.png"
images[2] = "images/opendays/002.png"
images[3] = "images/opendays/003.png"
images[4] = "images/opendays/004.png"
images[5] = "images/opendays/005.png"
images[6] = "images/opendays/006.png"
images[7] = "images/opendays/007.png"
images[8] = "images/opendays/008.png"
images[9] = "images/opendays/009.png"
images[10] = "images/opendays/010.png"
images[11] = "images/opendays/011.png"
images[12] = "images/opendays/012.png"
images[13] = "images/opendays/013.png"
var myimage = images[rand1]
document.write('<IMG src="' + myimage + '" ALT="The Trolleybus Museum at Sandtoft">')