This option enables you to specify the doctype that is used while editing content within TinyMCE, this defaults to .
Example of usage of the doctype option:
tinyMCE.init({
...
doctype : "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">"
});