For some reason Firefox does not display full feeds for WordPress blogs so let’s hack into the system and “force” Firefox to display the entire feed, including images. Now, we are messing up with the system core, so I suggest you save another copy of this file with another name in your computer. Once finished, upload it and change the name back to its original. If for some reason, does not work for you, upload the original file without changes (I use Cute FTP because I can have both local and remote sites open, edit any file and download and upload as I please)

This tweak  is good for RSS 2.0 Feeds (default wordpress format)

1. Open file

wp-includes/feed-rss2.php

2. Find following lines

<?php if (get_option('rss_use_excerpt')) : ?>
<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
<?php else : ?>
<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>

3. Now comment out last line. You can remove it too but commenting is a safe option. So it will look like…

<?php if (get_option('rss_use_excerpt')) : ?>
          <description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
<?php else : ?>
          <!- -
           <description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
          - ->

4. Save. You are done

If you use feedburner, ping it here to clear the cache

Thanks to DW for the tut. He offers other hacks for more feeds, go here to see them