To delete the style rule that you have applied to a tag, a class, or an ID in your page, select the style in the Styles view, and then select Remove from the pop-up menu. (You can also select the Remove selected rules button in the Styles view toolbar.) This deletes the style rule and will affect any other elements using the style rule.
To remove a class style from an element, select the element, and then in the Properties view, delete the class in the Class field.