Photo credit: Danika Bannasch, UC Davis. Hereditary equine regional dermal asthenia (HERDA) is a genetic skin disease found in the Quarter Horse. The disease is characterized by hyperextensible, elastic skin, severe dermatologic lesions, and often scarring along the back and withers of affected horses.
Contents. 1  Introduction to style sheets. 2  Adding style to HTML Setting the default style sheet language. 3  External style sheets Preferred and alternate style sheets.  Cascading style sheets Media-dependent 1  cascades. Hiding style data from user agents.  Linking to style sheets with HTTP headers.
The doctype declaration should be the very first thing in an HTML document, before the <html> tag. The doctype declaration is not an HTML tag; it is an instruction to the web browser about what version of the markup language the page is written in. The doctype declaration refers to a Document Type Definition (DTD).