Does a citizen of a third world country required to have a canadian tourist visa though he/she been living in the US for almost 4 years and currently holding a H4 visa? I will trully appriciate the replies... tnx a lot and have a nice day... :)

Short and sweet answer: yes.

Even if you want to go for a day to see niagara falls. Check canadian embassy website for more details.

This official site gives the requirements for third country citizens presently residing in USA, i.e. TEMPORARY RESIDENT VISA APPLICANTS WITH TEMPORARY STATUS IN THE US, to obtain Canadian - Temporary Resident Visa:

Consulate General New York :: APPLICATIONS AND GUIDES :: Temporary Resident Visa (http://geo.international.gc.ca/can-am/new_york/visas/temporary_resident_visa-en.asp#US)

My sister is on H4 visa and my brother in law is on H1 visa ( valid for three years) but they do not have any stamping on their passport. Can then visit to Canada and if yes for how my days . Please reply. And sure there will not by any problem for them to go back to USA

Thanks
Sachin