about:blank not rendering
As far as I can tell, Firefox is not rendering about:blank under certain conditions.
I am using "chrome\userContent.css" to customize about:blank, but sometimes Firefox is producing a blank white screen instead.
When opening a new window and sometimes when a new tab is created by closing the last one in a window, this style is not applied. "Tools > Page Info" confirms that the unstyled page is indeed about:blank. Also opening the developer tools to the "Style Editor" or viewing the page source will fix the issue.
Alle svar (2)
Some additional weirdness, if I point the homepage at an HTML file that contains a <meta http-equiv="refresh" content="0;url=about:blank">. It exhibits the same issue; sometimes about:blank renders without respect to the userContent.css. However if I change that to refresh after 1 second delay, the always renders correctly.
This appears to be a known bug (#1422507) since v57.