var h1 = document.getElementsByTagName('t')[0],
seconds = 0, minutes = 0, hours = 0,
t;

function add() {
seconds++;
if (seconds >= 60) {
seconds = 0;
minutes++;
if (minutes >= 60) {
minutes = 0;
hours++;
}
}

h1.textContent = (hours ? (hours > 9 ? hours : "0" + hours) : "00") + ":" + (minutes ? (minutes > 9 ? minutes : "0" + minutes) : "00") + ":" + (seconds > 9 ? seconds : "0" + seconds);

timer();
}

function timer() {
t = setTimeout(add, 1000);
}
timer();
/* We're always watching */