There are a few HTML items in active.asp that could be changed to improve the HTML validation:
There are two </tr> in a row, to fix, change lines 570-576
	if fDisplayCount = 0 then
		Response.Write	"              <tr>" & vbNewline & _
				"                <td colspan=""" & aGetColspan(7,6) & """ bgcolor=""" & strForumCellColor & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """><b>No Active Topics Found</b></font></td>" & vbNewline
	end if
end if
Response.Write	"              </tr>" & vbNewline & _
		"            </table>" & vbNewline & _
to
	if fDisplayCount = 0 then
		Response.Write	"              <tr>" & vbNewline & _
				"                <td colspan=""" & aGetColspan(7,6) & """ bgcolor=""" & strForumCellColor & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """><b>No Active Topics Found</b></font></td>" & vbNewline & _
				"              </tr>" & vbNewline
	end if
end if
Response.Write	"            </table>" & vbNewline & _
Line 481 is missing a </font> tag, change:
					"                <td height=""20"" colspan=""6"" bgcolor=""" & strCategoryCellColor & """ valign=""middle""><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><a href=""default.asp?CAT_ID=" & Cat_ID & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><b>" & ChkString(Cat_Name,"display") & "</b></font></a> / <a href=""forum.asp?FORUM_ID=" & Forum_ID & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><b>" & ChkString(Forum_Subject,"display") & "</b></font></a></td>" & vbNewline
to
					"                <td height=""20"" colspan=""6"" bgcolor=""" & strCategoryCellColor & """ valign=""middle""><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><a href=""default.asp?CAT_ID=" & Cat_ID & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><b>" & ChkString(Cat_Name,"display") & "</b></font></a> / <a href=""forum.asp?FORUM_ID=" & Forum_ID & """><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """ color=""" & strCategoryFontColor & """><b>" & ChkString(Forum_Subject,"display") & "</b></font></a></font></td>" & vbNewline
The script tag on line 611 could include the language and type:
		"    <script>" & vbNewline & _
change to
		"    <script language=""JavaScript"" type=""text/javascript"">" & vbNewline & _