var mess = new Array(
'<img src="/images/entetes/1.jpg" alt="Un professionnalisme sans faille" />',
'<img src="/images/entetes/2.jpg" alt="Une approche humaine" />',
'<img src="/images/entetes/3.jpg" alt="Une technologie performante" />');



var max = mess.length;
var num = Math.floor((Math.random() * max));
document.writeln(mess[num]);