How to Write streamingAssets folder files to webgl persistent data at run time?

hi every one, I've an problem with streamedassets. In my project i've an streamed asset folder. In that i have an upto 20 configuration files. I need to copy (write) that files to persistent data in webgl. I've tried many ways with WWW,but its getting file not found exception on browser console.Its working fine in Editor but problem raising on builded file. What i've to do. Please tell me. Sorry for my english. Thanks in advance.