Numerous 404 errors

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I am receiving numerous 404 errors when I do the following:

1. 400 Error — Sidebar Recent Posts widget: clicking on listed post (only one listed at this time)

Your browser sent a request that this server could not understand.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

2. 400 Error 00 At the bottom of the page ther are 3 buttons ‘Alternative Medicine’ and ‘Comments’ and Edit. Clicking Comments will cause the 404 error. There are currently no comments.

I feel that the errors are related in some way. Do you have any ideas, how I can fix this.

boblan66 ??