WP 1.5 wp-rss2.php etc. wont validate

Am newbie and just learned that WP automatically creates feed pages.
But I find they dont validate, some later display 404…. at feedvalidator.org
Here are three error pages if anyone can give simple explanation how to fix…
(shouldn’t these be automatically working?)
Many thanks

feedvalidator.org

1. http://ayurvedahc.com/shakti/wp-atom.php

• Feeds should not be served with the “text/html” media type [help]

• line 1, column 0: Undefined root element: br [help]

• line 2, column 0: XML parsing error: <unknown>:2:0: junk after document element [help]
<b>Parse error</b>: parse error, unexpected T_STRING in <b>/home/virtual/si

2. http://ayurvedahc.com/shakti/wp-rss2.php
– length must be positive integer currently showing length=”
– type attribute of enclosure must be a MIME type currently showing: type=”
– item contains more than one enclosure

3. http://ayurvedahc.com/shakti/wp-comments-post.php
• line 1, column 0: XML parsing error: <unknown>:1:0: no element found [help]

4. http://ayurvedahc.com/shakti/wp-commentsrss2.php
• Feeds should not be served with the “text/html” media type [help]

• line 13, column 26: webMaster must include an email address [help]
<webMaster>[email protected]</webMaster>