I used to run into the problem of having warning messages pop up when I accessed a page with secure and non-secure information and finally I found something that let me post non-ssl encrypted content on an ssl encrypted page and no warning messages will pop up!

On on of my secure sites, lets say https://www.askapache.com/htaccess/ I wanted to give my visitors the option to post youtube videos and google videos. But then everyone kept seeing the "warning, mixed secure/non-secure content" on a page that had one of these videos.

I basically did a str_replace on all posts text for http://video.google.com and http://youtube.com to change them to https://www.example.com/htaccess/ Then I used the following rewrite code:
RewriteEngine On
RewriteBase /
RewriteRule ^htaccess/googleplayer.swf(.*)$ http://video.google.com/googleplayer.swf$1 [L]
RewriteRule ^htaccess/youtube/(.*)$ http://www.youtube.com/$1 [L]
and it worked! But one caveat, this wouldn't turn the warning messages off in IE < version 7, so I added some simple HTML to the head of all my pages that only show up for people using IE < version 7.
<!--[if lt IE 7]>
<span id="ie7">Please Upgrade:
<a href="http://www.microsoft.com/windows/ie/downloads/default.mspx?mg_id=10013">IE 7!</a>
<a href="http://www.mozilla.com/en-US/">FF!</a></span>
Cool huh! Fix for secure and nonsecure items warning message