sillypighui

i keep having these white stains on my bathroom floor tiles when it dries. i have tried all means to scrub it off but it's still there when the floor dries. what's the root of the cause? Is there any way I can get rid of it and pevent it from coming back? the pictures can be found here http://www.flickr.com/photos/kwanwei/sets/72157623222912019/