For example, developers of websites can test if a site is correctly displayed, if it is readable, etc..
There is the iPad simulator (perhaps the best) present on http://alexw.me/ipad2 showing some applications such as: iPod, iMovie, Clock, Safari, etc..
Or there is an online emulator of an iPad suitable only to view websites!
See the: http://ipadpeek.com and http://ipad-emulator.org by which you can surf internet perceiving the same perspective you would have using a real iPad (with them you can rotate vertically or horizontally the virtual iPad).
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