http://schulich.ucalgary.ca/chemical/graduate/faq#q17aarun_kumar said:no i sent it in my college's letterhead......is it bad!
check this link, this is about my course (Petroleum Engineering) , there is a question "Can I use any form for the letters of reference? " check the answer for that FAQ
In my course i have to download reference form and make my referee to feel that and seal it in my university envelope with university stamp and his signature
so find out about your course...