Tips from here.
nglayout.initialpaint.delay— Set the integer value to
0if the connection is too slow.
E., 06.12.2010 Edit/Update: The downside is greater CPU usage, so if the computer is slow and/or if there's a slow operating system (Windows 95/98), then don't use this feature.
For example, I have at my wherewithal a 900 MHz computer with 128 Mb RAM and Windows 98SE (the operating system that was supplied by the manufacturer), in which OS the latest Gecko-based browsers can be Mozilla Firefox 18.104.22.168, K-Meleon 1.5.4 and SeaMonkey 1.1.19.
In late 2010 I realized how much more complex have websites become and their rendering really slowed the computer down. Messages about unresponsive scripts have also become more frequent.
The only thoughtful solution to this would be changing the operating system to something lightweight, which supports SeaMonkey 2.0 (such as Linux). More about this in a future post.