If Scotland wins her independence one day, it will be necessary to assign a ccTLD (country-code top-level domain) instead of .uk. A ccTLD always consists of exactly two lower-case letters without any accents.
However, there are so many countries in the world that there aren't many options left.
The most natural one would be .sc, I guess, but that's the Seychelles. .sl? No, that's Sierra Leone. .so? .st? .sa? .sn? .sd? Nope, that's Somalia, São Tomé and Príncipe, Saudi Arabia, Senegal and Sudan, respectively.
Hmmm, so what about basing it on the Gaelic name for Scotland, Alba? Well, .al is Albania, and .as (for Alba/Scotland) is American Samoa, but .ab is actually free, so I guess that would be the most obvious ccTLD.