myLine = 4;
myMes = new Array(
"<img src=\"images/title1.jpg\" width=\"740\" height=\"110\" border=\"0\" alt=\"\">",
"<img src=\"images/title2.jpg\" width=\"740\" height=\"110\" border=\"0\" alt=\"\">",
"<img src=\"images/title3.jpg\" width=\"740\" height=\"110\" border=\"0\" alt=\"\">",
"<img src=\"images/title4.jpg\" width=\"740\" height=\"110\" border=\"0\" alt=\"\">"
);
myRnd = Math.floor(Math.random()*myLine);
document.write(myMes[myRnd]);