I've already looked for something that will allow users to customize their CSS styles without overwriting problems during automatic updates.
By now, I've found nothing, and the only way I see to do things are :
- you shouldn't edit anything in the plugin folder. The upgrade process will overwrite any edits that you make.
- to define and use your own CSS rules, create a new .css file in your theme's folder and include that in the theme after the call to wp_head().
- Add to this file all the CSS rules you need. These rules will overide the plugins initial rules.
So if you do that, next update should be less painful for you. If someone here knows a better way to proceed, it would be nice to share it with us !
I hope this will help you. Let us know, I know other users have hed the same problem!
For IE8, see the [FAQ](http://wordpress.org/extend/plugins/wp-parallax-content-slider/faq/)