Users cant add code to post problem, on multisite

Hi, i noticed that when i am loged in as user on my ms network i cant add html or iframe to posts, i put code to post and save it and it only dissapear!! but when i am login in as network administrator i go to that same post on someones blog and add code and it works normaly. what can be problem, its like that adding code to posts is disabled for users, i dont even try to do this, who to solve that?