As for "convenience URL", do you type "altavista.com" or "av.com"?
I have one three-letter abbreviation for one of my domains (15 characters-dot-something) - it's very very few users that actually use it. Less than 1% of the users that type in the 15 chars.
Also, they're kinda hard to promote, as you don't really want to link to them anywhere if it's not the right domain name.
>> wise to create...
If you're thinking about the "tinyurl" type services, it wouldn't be:
[webmasterworld.com...]
If you want to do this, make 100% sure that it always redirects to the main using a 301 status code (see apache forum for that).
When it comes to making a memorable impression in offline promotions, I think there's plenty of room for this approach - maybe even an advantage. I had no problem remembering the phrases when I got to my computer, even though I had no way to make a note to myself at the time.
Shorter the better otherwise people will just rely on Google or MSN "to guess it for them"
The rules for domains are
A valid domain name can have 63 characters (excluding the extension).
It used to be 26 including the extension. I think the change occurred about Jan 2000
I'm not totally sure what an "octet" is, but i guess it's the binary representation of a single character - correct me if i'm wrong. A "label" is what is between any two dots.
So, the FQDN is 255 while any item between two dots is 63, it seems.
Host names, OTOH, can have up to 255 characters (RFC 1123)
This means that you can have a host name that is too long to become a domain name (ie. a "label" in a FQDN).
Some operating systems and software might not support all this, though.