Like the other LTS point releases, Ubuntu 10.04.3 LTS just incorporates the latest stable release updates and bug-fixes that have been introduced since the April 2010 release of the "Lucid Lynx". The Ubuntu 10.04 LTS build is still supported for desktops and servers on i386 and x86_64 architectures.
Numerous updates have been integrated, and updated installation media have been provided so that fewer updates will need to be downloaded after installation. These include security updates and corrections for other high-impact bugs, with a focus on maintaining stability and compatibility with Ubuntu 10.04 LTS.
Read more and download Ubuntu 10.04.3 from the release announcement.