linux - How to delete folder of owner/group 99 99

I am using wordpress with wp-super-cache plugin. This plugin automatically created a cache folder in my site for storing the cached files.

But unusually it created folder with owner/group 99 99. It was created automatically.

Due to this, i am not able to delete that folder or change the CHMOD of that folder. This really a headache. I searched google, but none gave me a good answer.

Please help me delete or change the CHMOD of that folder ?

I am on Linux server.