What are the valid chars in a domain name ?

[jehoshua]

Hi,

Strange question, but then, I'm a strange person.

Hmm, practical example,........ so for instance we wanted a new domain and wanted to call it:

stereos&amplifiers.com

is that allowed, ..... an ampersand ?

I've seen a dash "-" used, I think an underscore "_" , but never seen an ampersand or I don't think I've ever seen a period "." , in a domain name.

Obviously a to z and 0 to 9 are okay.

Can someone please advise.

Peter