When you're out of range and using ranged based attacks, or things line of sight you against small objects, your "auto attack" skills typically disable themselves,
Also, if you're not in range and getting floating combat text errors, try glancing at your actual skills and observing your range, to get an idea of when you are at certain distances.
The best way is to simply look at the number.
It turns white when you have something targeted when it is in range,
and red when you have something target, that is not in range.
This actually happens with melee based skills somewhat as well, and medium or short range skills. It's part of paying attention to what your character is doing.
Also, if you're not in range and getting floating combat text errors, try glancing at your actual skills and observing your range, to get an idea of when you are at certain distances.
The best way is to simply look at the number.
It turns white when you have something targeted when it is in range,
and red when you have something target, that is not in range.
This actually happens with melee based skills somewhat as well, and medium or short range skills. It's part of paying attention to what your character is doing.