where can i find to make this txt smaller
because there so big
also when you open a product become real big like to have a normal size
this code is in style.base.css in basic/customer/ folder inside your skin.
.mainbox-title span {
color: #2D2E2E;
font: bold 200% Arial,Helvetica,sans-serif;
}
try lowering the 200% size value to 160 or 132.