Document Type Definition (DTD)
According to the XHTML 1.0 W3C recommendation (http://www.w3.org/TR/xhtml1/) section 3.1.1, there must be a DOCTYPE declaration in the document prior to the root element.
The public identifier included in the DOCTYPE declaration must reference one of the three Document Type Definitions found in http://www.w3.org/TR/xhtml1/#dtds using the respective Formal Public Identifier. The system identifier may be changed to reflect local system conventions.
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/DTD/xhtml1-strict.dtd">
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
"http://www.w3.org/TR/DTD/xhtml1-frameset.dtd">
LANSA for the Web ships with default pages for each of these Document Type Definitions.
If you download the Document Type Definitions and install them on your web server, then you can change the DOCTYPE declarations so you don't need to refer to the w3.org web site.
Note: LANSA for the Web uses either the Transitional DTD or the Frameset DTD (for pages that contain frames). It does not use the Strict DTD, as strict XHTML requires that all style information be provided via style sheets and not embedded in the XHTML page.
Some old browsers may have problems avoiding the display of the DOCTYPE declaration. Current generation browsers correctly hide them from being displayed.