Validation Interpretation: Please help

Dear Sir/Ma'am:

I am down to just six lines of code that will not validate on this site:

http://dkc.mse.jhu.edu/~cyork/dkcsite/template.html

Would you please tell me what's wrong with the six invalid lines that all 
appear to
be related?

Below are the results of checking this document for XML well-formedness and
validity.
**Line 45, column 5:
  <tr />
       ^
Error: missing a required sub-element of "tr"

** Line 45, column 5:
  <tr />
       ^
Error: missing a required sub-element of "tr"

** Line 46, column 13:
  <td width="3"></td>
               ^
Error: element "td" not allowed here; assuming missing "tr" start-tag

** Line 107, column 50:
  ... ence news briefs with a link to each full article"> 
                                                        ^
Error: element "table" not allowed here; possible cause is an inline element
containing a block-level element

** Line 131, column 7:
  </table></div>
         ^

Error: end tag for "tr" omitted; end tags are required in XML for non-empty
elements; empty elements require an end tag or the start tag must end with "/>"

** Line 46, column 0:

<td width="3"></td>
  ^
Error: start tag was here

Thank you for your response.
Cynthia

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