Looking for details on when to use / not-use XHTML 1.0 vs. XHTML 1.1 DTD.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
Reference link: http://www.w3.org/QA/2002/04/valid-dtd-list.html