var imgarray = new Array()
imgarray[0] = 'machine_strip'
imgarray[1] = 'machine_strip_1'
imgarray[2] = 'machine_strip_2'
imgarray[3] = 'machine_strip_3'
imgarray[4] = 'machine_strip_4'

var selimage = Math.round(Math.random()*(5-1));
document.getElementById('idximg').src="images/"+imgarray[selimage]+".jpg";