1. In-line styles - these are included in the HTML tag as style attributes.
2. Document level styles (textbook: Embedded & global styles) - these are
styles listed in the "Head" tag and effect the entire document.
3. Linked or external style sheet - these are general style sheets that are
usually used for an entire web application. They are located in a separate file
and inserted into the document using the "link" tag.
Style hierarchy is as follows:
In-line takes precedence over document level, which takes precedence over
external, which takes precedence over browser.