[oast]

You could use .htaccess and mod_ReWrite to 'simulate' the use of .htm/.html files.

To use .php extensions as .html put these lines in your root .htaccess file

RewriteEngine On
RewriteBase /
RewriteRule ^thisfolder/thispage.html$ /thisfolder/thispage.php

That way your thispage.php can have php script running, but be named as thispage.html without impacting the server performance with other .html extensions

I'm not recommending it as a way of avoiding being blacklisted for using scripts, but as a way of being consistent with your page extensions.

Question 2:
As long as the flash banner doesn't take an age loading (most are smaller than animated gifs anyway) and it doesn't distract from the content on the page, then there would be no problem with me. Bear in mind there are a few users that cannot see flash animations, whereas 100% of people (with images enabled) will see the .gif files