var names = new Array();
names[0] = 'abs';
names[1] = 'reyes';
names[2] = 'minas';
names[3] = 'eiffel';
names[4] = 'bh1';
names[5] = 'bh2';
names[6] = 'cit1';

var name = Math.round(Math.random()*(names.length-1));

function getBackground() {
    document.write("\
<style type=\"text/css\">\
<!--\
#header { background-image: url(images/header_"+names[name]+".jpg);}\
#menu   { background-image: url(images/header_menu_"+names[name]+".jpg);}\
-->\
</style>");
}