When you create a new page, you can make it XHTML-compliant. You can also make an existing HTML document XHTML-compliant.
To create a new, XHTML-compliant document:
Select File > New.
The New Document dialog box appears.
Select a document type.
Select the Make Document XHTML Compliant option.
Note: Not all document types can be made XHTML-compliant.
Click OK.
To create XHTML-compliant documents by default:
Select Edit > Preferences or Dreamweaver > Preferences (Mac OS X) and select the New Document category.
In the New Document category, select a document type and select the Make Document XHTML Compliant option.
Click OK.
To make an existing HTML document XHTML-compliant:
Open a document, then do one of the following:
For a document without frames, select File > Convert > XHTML.
For a document with frames, select a frame and select File > Convert > XHTML. To convert the whole document, repeat this step for every frame and the frameset document.
Note: You can't convert an instance of a template, because it must be in the same language as the template on which it's based. For example, a document based on an XHTML template will always be in XHTML, and a document based on a non-XHTML-compliant HTML template will always be HTML and can't be converted to XHTML or any other language.