I totally understand that sometimes you just live an area that doesn't have a shop for miles or they have no idea what they are doing and therefore buying boots over the internet is your main option. With that said, however, you need to be aware that there are some really big risks you take with the boot not properly fitting you. What will happen is that you will probably pick a boot that is too big (because it feels comfy in your living room) but after skiing it for a few days you will find that your heel moves and you'll get blisters or you are getting a bit of shinbang. This is a very common scenario.
If you can't get to a good local shop, then perhaps wait until your next ski trip and find some boots at/near the resort where you go. Chances are this will be a lot better than buying a boot online.