Description of problem:
Fields on the new sign up page have no prompt, so if invalid characters are entered the user won't know until they've moved on to the next field.
Either have an indicator, or validate on key up.

Version-Release number of selected component (if applicable):
3.4.0-snapshot

How reproducible:
Easy always

Steps to Reproduce:
1. Press sign up to go to the register page
2. Click on username, and enter te$t
- No validation
3. Click elsewhere on the page

Actual results:
Validation has occurred after the user has left the page

Expected results:
Either in the field itself (e.g. greyed out a-z,0-9,_ pretext) or as an (i) mouse over, at least something should be displayed. Or at least validate while they type.

Additional info:
These indicators existed in a previous version.