What are the constraints that Gmail puts on email signatures?
I'm trying to create a simple HTML table signature that users can copy and paste into Gmail's signature section, however I keep running into the "Sorry, the signature for  is too long. Please try a shorter signature" error.
I'm aware of the 10,000 character limit, but the total HTML character count is much less than that.
If I delete a few of the images or some of the text from the signature I can get it to pass this constraint, however the signature is practically rubbish because of the deleted content.
I've tried to trial and error it to find a pattern to understand the rules, but nothing is emerging yet. Certainly, deleting big chunks of HTML from the signature has no effect.
So, does anyone know the restrictions (character, HTML, images, or otherwise) that Gmail is referring to when it throws this error?