Yahoo Code appearing at the bottom of Posts to a certain Yahoo Group - How do I get rid of this?

The script is included at the end of the post. The script appears at the bottom of posts to a certain Yahoo Group.

If I send an E-Mail to another person's E-Mail address, the E-Mail they receive does not contain the script.

How do I eliminate this?

It is set up as plain text - no html.

Example (This is the actual script):

<!--

#ygrp-mkp{

border:1px solid #d8d8d8;font-family:Arial;margin:14px 0px;padding:0px 14px;}

#ygrp-mkp hr{

border:1px solid #d8d8d8;}

#ygrp-mkp #hd{

color:#628c2a;font-size:85%;font-weigh... 0px;}

#ygrp-mkp #ads{

margin-bottom:10px;}

#ygrp-mkp .ad{

padding:0 0;}

#ygrp-mkp .ad a{

color:#0000ff;text-decoration:none;}

-->

<!--

#ygrp-sponsor #ygrp-lc{

font-family:Arial;}

#ygrp-sponsor #ygrp-lc #hd{

margin:10px 0px;font-weight:bold;font-size:78%;line-...

#ygrp-sponsor #ygrp-lc .ad{

margin-bottom:10px;padding:0 0;}