Error message appears

Warning: Cannot modify header information – headers already sent by (output started at /home/yogaclas/public_html/wp-config.php:153) in /home/yogaclas/public_html/wp-includes/pluggable.php on line 850

I keep getting this message and sometimes I can even connect to my site and external links to http://www.yogaclasses.ie/ don’t work. This started ever since I tried to install a plugin called ‘comment karma’. I had to put the code into the header but that didn’t work so I removed it.

I have had this message since

PLEASE PLEASE PLEASE help……