I would like to limit download speed in my 4 Mb network in a way that each user could achieve only 1 Mb for downloading. I have made a queue that really limits the bandwith with packet marking on a postrouting chain but it does not work as I expected. It limits total bandwith for all hosts so all computers heve to deal 1 Mb between each other. I would like to do it in a way that every host could reach 1 Mb but not more.
Can anyone help me

Have a look into PCQ; This should meet your requirements:

http://wiki.mikrotik.com/wiki/Manual:Queues_-_PCQ