Hi, I am using:

.dijitTooltipContainer {
position:absolute;left:0;top:0;
background-color:#CCD9FF;
border:1px solid gray;
max-width:450px;
font-size:smaller;
}

just to check if that is correct way to customize it.
i tried the dojo book's way, like .dojoTooltip, .dijitTootip, they don't work.