Your ski boots are THE most important piece of ski equipment you own.
— Shannon Bahrke Happe, 3 Time Olympian, 2 Time Olympic Medalist, Moguls

A good fitting ski boot is an extension of your leg/foot.  When you buy a ski boot, it is HIGHLY RECOMMENDED that you visit your local ski shop to get a professional boot fitting.  A good boot fitter will take foot measurements, assess ski specific biomechanics.  They will also investigate custom boot liners and inserts that are modified to fit your foot perfectly.  Lastly, the will dial in the fore/aft and canting of the boots.

The moral to the story...

DO NOT BUY BOOTS ONLINE!