Help with XHTML validation

Can anybody help me with this? I don’t know how to fix it. it happened when I tried to validate the site.

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• Validation Output
This page is not Valid XHTML 1.0 Transitional!
Result: Failed validation, 1 Error
Address:

Encoding: utf-8

Doctype: XHTML 1.0 Transitional

Root Element: html
Root Namespace: http://www.w3.org/1999/xhtml

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Validation Output: 1 Error
1. Line 29, Column 18: document type does not allow element “div” here; missing one of “object”, “applet”, “map”, “iframe”, “button”, “ins”, “del” start-tag.
<div id=”subtop”>writing for local people</div>
✉
The mentioned element is not allowed to appear in the context in which you’ve placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you’ve forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as “<p>” or “<table>”) inside an inline element (such as ““, “<span>”, or “<font>”).