Ajax Collapsible Panel / Modal Popup Flicker on pageload fix

The Modal Popup Extender and the Collapsible Panel Extender sometimes cause the screen to flicker on page load. To solve for this do the following.

Modal Popup
Set the style property display to 'none'

Collapsible Panel Extender
Make sure the extender has SuppressPostBack="True", and on the panel itself set the Height="0px" and a style property overflow:hidden;