Code
<script language="JavaScript1.2">
var message="Название сайта" //specifys the title
var message=message+" " //gives a pause at the end,1 space=1 speed unit, here I used 10 spaces@150 each = 1.5seconds.
i="0" //declares the variable and sets it to start at 0
var temptitle="" //declares the variable and sets it to have no value yet.
var speed="150" //the delay in milliseconds between letters

function titler(){
if (!document.all&&!document.getElementById)
return
document.title=temptitle+message.charAt(i) //sets the initial title
temptitle=temptitle+message.charAt(i) //increases the title by one letter
i++ //increments the counter
if(i==message.length) //determines the end of the message
{
i="0" //resets the counter at the end of the message
temptitle="" //resets the title to a blank value
}
setTimeout("titler()",speed) //Restarts. Remove line for no-repeat.
}

window.onload=titler
</script>

Пример: