When editing a CSS style in the visual editor's change list (for example, after making a color change), you'll see a drop-down menu at the bottom of the Edit style dialog with two options.
After making your change you have two options:
- Add a CSS rule means that the style change will be installed as a CSS rule targeting the element. The element doesn't need to exist when the tag runs. This may not always work if the element sets the style value explicitly.
- Change Element style means changing the style of the element directly. This requires the element targeted to be present when the tag runs.
The Important checkbox adds the "!important" attribute to the style to override other declarations. Learn more.