error on line 2 at column 6: XML declaration allowed only at the start of the do

Hello,
I have error in genrated xml file,

This page contains the following errors:
error on line 2 at column 6: XML declaration allowed only at the start of the document

I have checked with disabling cache and SEO plugins but error still exist.

http://prntscr.com/jshtwb

please give the solution for this.

Thanks,
Rasik