The answer to that question is a solid “yes” and “no”.
Yes, usually, a desktop layout will kind of work on the iPad. But because desktop layouts are not optimized for touch, the user experience can be pretty poor. The reason is mainly because of the size of the fields and buttons. When clicking by using a mouse, these buttons and fields can be small, but for iPad, you want buttons that are anywhere from 30-50 points high to make them touch friendly. But if you are accessing it using FM Go, it can actually work in a pinch. Note that some scripts related to printing and window control may or may not work, depending on what you are trying to do.
But, No, you really will not enjoy using it on an iPad unless the layouts have been optimized for touch. It is a so much more satisfying experience to touch into fields which are large enough to tap into. It’s the same with buttons; they are much better when they are large enough to be easily tap-able.
The real test is the ‘fat finger challenge’. Can someone with stubby fingers easily use the app on an iPad? That is the real test! So find someone on your team with fat fingers and let them try it!
What we like to do is either build a hybrid layout, which works great for iPads and will also work for desktops using a mouse. And if you want to really customize, we can make the system smart enough to know if you are using the application on an iPad, or on a desktop (or browser), and take you to the correctly developed layout for that type of device.