limiting the download

how can i limit the download of users ??
and how can i sure that no netcut is used ??

You need to supply more information!

Are these hotspot users? Are these directly connected LAN users? Are these PPPoE Users? Do you want to limit speed? Do you want to limit total amount of MB downloaded??? Both?

i used hotspot users and connected directly to LAN
i have a line 4 MB and i want to ensure that it not exceed 512KB fro each user

With Usermanager:
http://wiki.mikrotik.com/wiki/User_Manager/Limiting

Without Usermanager:
Put the rate limit in the Hotspot Server Profile