The HTML Rewriting preferences determine what Dreamweaver does while opening HTML documents. These preferences have no effect when you edit HTML in the HTML Source inspector. If you turn off these rewriting options, Dreamweaver displays invalid markup items in the Document window for HTML that it would have rewritten. If you are importing an HTML document from Word, you can use the Clean Up Word HTML command to strip out any unnecessary HTML code. See Cleaning up Microsoft Word HTML for more information
Fix Invalidly Nested and Unclosed Tags Rewrites invalidly nested, or overlapping, tags. For example, <b><i>text</b></i> is rewritten as <b><i>text</i></b>. This option also inserts closing quotation marks and closing brackets if they are missing.
Remove Extra Closing Tags Deletes closing tags that have no corresponding opening tag.
Warn when Fixing or Removing Tags Displays a summary of technically invalid HTML that Dreamweaver attempted to correct. The summary notes the location of the problem (using line and column numbers) so that you can find the correction and ensure it is rendering as intended.
Never Rewrite HTML: In Files with Extensions Allows you to prevent Dreamweaver from rewriting HTML in files with the given file name extensions. This option is particularly useful for files of types that contain third-party tags (such as ASP tags). For more information, see Avoiding rewriting third-party tags.
The two Special Characters options allow you control over whether Dreamweaver encodes certain characters in certain contexts. In general, it's best to leave these options selected unless your files contain certain third-party tags that use the characters in question. For more information on these options, see Avoiding rewriting third-party tags.