But the smaller screen on mobile devices sets a different constraint. On a PC, you are pretty safe assuming say, a minimum resolution of 800x600, 1024x768 [1],

But the smaller screen on mobile devices sets a different constraint. On a PC, you are pretty safe assuming say, a minimum resolution of 800x600, 1024x768 [1], and generally software can just move autoresize to shift UI widgets to make use of additional space. On the other hand, for mobile devices, with resolution of say 320x480 (iPhone/iPod touch) vs. 1024x768, you need to be much more specific with the UI to make efficient use of the space. E.g you find that good apps running on the iPhone often have different looking counterparts on the iPad. Add to it things like certain devices having touchscreens, vs. non-touchscreens for Android which affects the entire UI and even nature of the software, it makes handling such variations much more difficult than for the PC market. [1] Unless you are writing software for very specific purposes that need to utilize the whole screen efficiently, then we are back to the same problem.