Adobe files are not backwards compatible.
If you want to open it in CS5, you would need to use the “Save a copy as CS5.5” Then you would need a copy of CS5.5, open the project and “Save a copy as CS5”
Any effects that aren’t in the CS5 version would be listed as missing, but when you go forward again, they would be return with the original parmaters used, ie..warp stabilizer wouldn’t show up in CS5(missing), but if saved the CS5 project and opened it up later in CS6 it would return it would return with the original settings you used in the initial project.
Johnny Cuevas, Editor
Thinkck.com
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.