Many times you need to see how your website or blog look may in iPad. For that buying iPad is costly affair. You may be very interested or not about how your website look in iPad depends on type of website you are running. For non transactional website everything fall on place is not that important. Instead you just want your website look decent in iPad. For that online iPad simulator is good enough and easy solution if it shows near to the actual ipad look.
I have found output from ipad-emulator very near to the actual. Even it looks exactly but I have not tested it on many pages so I am not very sure about how it fares on different HTML elements.
Another ipad simulator which looks good is ipadpeek.