Startfox 9.13, the latest build is 100% Vista compatible due to a new part of AutoConfig1:
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if exist %systemdrive%\Users\ copy c:\progra~1\AppomattoxSoft\Startfox\bin\autoconfig1\nt6\*.* c:\progra~1\AppomattoxSoft\Startfox\opt\menu
if exist %systemdrive%\Users\ regedit /s c:\progra~1\AppomattoxSoft\Startfox\bin\autoconfig1\nt6\e.reg
if exist %systemdrive%\Docume~1\ copy c:\progra~1\AppomattoxSoft\Startfox\bin\autoconfig1\nt5\*.* c:\progra~1\AppomattoxSoft\Startfox\opt\menu
if exist %systemdrive%\Docume~1\ regedit /s c:\progra~1\AppomattoxSoft\Startfox\bin\autoconfig1\nt5\e.reg
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This basically says "if the folder Users exists, you are using Vista, therefore, implement the Vista patch.
It is built right in. No addendum patch or anything.
Acid2 is a W3C test for web standard compatibility. Firefox 2, being that web standard compatibility was not scheduled for Firefox until version 3, does not pass this test, however Firefox 3 does.
The test can be found here:
http://www.webstandards.org/files/acid2/test.html
The Acid3 Test, however, I am afraid Firefox does not yet pass. However, I have seen no browser yet that can.
Acid3 is located here: http://acid3.acidtests.org/