OK Guys, I appreciate your help. By looking at the source code of the Blank Page which gave the 500 Internal Server Error, I found the following comment:
<!-- SHTML Wrapper - 500 Server Error -->
I was able to successfully execute the PHP file by changing the permissions to 777 of:
/assets
/assets/mystyle.css.php
This is clearly a security restriction from my hosting provider (Justhost).
I’m going to automate this process by playing arount with Yii CAssetManager’s following properties:
newDirMode integer the permission to be set for newly generated asset directories.
newFileMode integer the permission to be set for newly generated asset files.