What is the maximum no of characters allowed in help text? I have a very long help-text for a field and I can only see a portion of it when I hover over the control.
the portion of your text you can see will most likely be the maximum allowed. I run a test and could enter 2^9 (=512) characters. Everything entered on top will be erased in your help window.
If you need to exceed this maximum you could try to create your own tooltip with jQuery and not use the buil-in one. this should give you something to start with: Simple Tooltip with jQuery (only text) - Alessio Atzeni
However, if you really need more than 512 characters as a tooltip, you should maybe think about rather providing a documentation for you form.
Retrieving data ...