If you're having some trouble saving your signature, you can try the following steps:
1. Sign into Webmail 2. Click Preferences in the top-right 3. Select General on the left 4. Switch to the Basic (HTML) option 5. Save your changes and sign out of Webmail 6. Sign back into Webmail, update your signature and save your changes 7. Switch back to Standard (AJAX) in the General section and save your changes
We've found that this will allow you to save your signature in most circumstances. We are aware of this situation and it has been submitted to our engineering teams to be resolved as soon as possible.