Thanks again for your answer Rob,I’m rally glad for your help. I’ve just read the modernizing config.lua article and some doubts about content areas are gone. I just want to ask: should I set my config.lua as infiSnyp suggest or should I use the 800x1200 layout to be sure my app will work in every android and ios device? Should I use a different config.lua for building apps for tablet and smartphone or can I use the same for both?
Thanks again 
Apple and Google really seem to want to keep things in 320 point based systems. Some people like the larger content area. I tend to stay with 320x480 myself, though I do use the Modernizing config.lua idea, just with the smaller define area for games. I understand that my things on the screen will likely move around and not be the same, fixed distance away from each other. Others want to make sure object B is 100 px a way from object A and that’s a bit harder to do with the Modernizing one.
Back to the size thing, if you’re going to be using the widget.* API’s you should certainly stay at 320x480 for now. They don’t scale for larger content areas.
If you’re building a business type app you might want to consider “adaptive” scaling. There are some blog posts on that as well. The gist here is that objects on the phone and on the tablet are going to be close to the same size. The config.lua above, your buttons and such on an iPad will visibly be 2-3 times larger than it appears on the phone. Adaptive will give you a 320x480 size on a phone and give you a 1024x768 size on a tablet allowing you to fit more stuff instead of just a zoomed up phone app. Of course this takes more work to make it look right
Rob
I’d like to set all of the objects in my game be x pixels away from each other. How can I do this? And which effect could I create if I let my objects “move around”?
Either method will let you position things fixed distances for objects. You might be better off just keeping your existing config.lua and just not have anything important in the bleed areas.
Rob
I’m using the aspectratio config.lua. I’ve just placed all of my objects and tried on smartphone emulator. It works nice.
I’ve executed the same code using an Ipad air emulator and I’ve noticed that all of the objects keep their coordinates while the dimensions change. Is there a way to keep proportions even if device changes? I mean…if I have a square object it should keep his dimensions and still be a square even in a rectangular screen, isn’t it?
Can you post your config.lua?
I’ve just modified my config.lua, and now everything works fine.
Thanks a lot for your support guys =)