Wow, we really need a FAQ on the projects pages to deal with these recurring posts. It's just stuff that gets asked quite a lot over and over, and get's lost in the depths of the forums. Not to pinpoint you out in particular, just frustrating to see the same question pop up again, and again...
Anyway, you need to change the xsl to allow the html to be displayed. There's a lot of reasons why RSS newsfeeds should not contain HTML, but that's falling on deaf ears, but if you do allow HTML, be aware that there are lots of security issues with blinding placing a feed with HTML on your production site, so test on non-production sites thoroughly before using them in production. End of Public Service Announcement.
So, here's what you do to allow it -
Make the change from this:
<xsl:value-of select="substring(description,1,10)" >
To this:
<xsl:value-of select="substring(description,1,10)" disable-output-escaping="yes"/>
The key component is to include the snippet - disable-output-escaping="yes" - wherever you need to allow for HTML to display.
Search my posts for full example xsl , and the forums for other similar posts.
Cheers