I am getting the warning:
Attribute minSdkVersion (3) is lower than the project target API level (8)
How will this affect my app?
You can safely ignore the warning.
It’s a weird warning – it means you are using tools for API level 8 (Android 2.2/Froyo) but targeting API level 3 (Android 1.5/Cupcake). That warning will always come up unless you you were using the SDK to target the Android release it coincides with – in this case, you would have to target Android 2.2 with your current SDK.
I do most of my development with the project set to the minSdkVersion level. That pretty much guarantees that I’m not using any more recent APIs. I then switch to my targetSdkVersion level before publishing the app. The only problem I’ve run into so far is that the lower level doesn’t support some manifest syntax that I need to use in production. (Level 3, for instance, doesn’t support targetSdkVersion.) I just fix up the manifest after switching to the higher level.
See also Dianne Hackborn’s response in this thread: