There is Ask bot, which sets this header:

Mozilla/2.0 (compatible; Ask Jeeves/Teoma) 

Considering this, I have the following questions:

• If I'm writing a web crawler named Goofy, what user agent should I use?
• What is the difference if I put Mozilla/2.0 or Mozilla/5.0 ?

Any other suggestions about how should I format my user agent to comply to the current standards are most than welcomed.

There is Ask bot, which sets this header:

Mozilla/2.0 (compatible; Ask Jeeves/Teoma) 

Considering this, I have the following questions:

• If I'm writing a web crawler named Goofy, what user agent should I use?
• What is the difference if I put Mozilla/2.0 or Mozilla/5.0 ?

Any other suggestions about how should I format my user agent to comply to the current standards are more than welcome.