The content of the document is Cascading Style Sheets.

Primary Heading

Secondary Heading

This line will be experimented on, so it will change its' appearance periodically.

Selector types:

1. id
2. class
3. tag or element

CSS Placement:

1. inline
2. internal
3. external

inline selector

This text is in blue color.

This text is in blue color with shades.

internal selector

This text is in green color.

external selector

This text is in yellow color with navy blue background.

selecting by id

This line will be experimented on, so it will have a border now.

selecting by class

This line will be experimented on, so it will change to orange color text.