what are you trying to limit it in?
if being pulled from SQL using a query, you can append this to the end of the query:
LIMIT $start,$total
where $start = the starting row, and $total is the total number of rows you want to show..
i.e. this line would show lines 50-125
LIMIT 50,75
if it's in a numbered array you can do
for ($n=$start;$n<$start+$limit;$n++) {
echo $array[$n];
//code, same numbering as above
}