The CSS source page editor lets you edit a cascading style sheet. The editor provides many text editing features, such as content assist, syntax highlighting, unlimited undo and redo, element selection and formatting, and document formatting. The CSS source page editor lets you edit a cascading style sheet. The editor provides many text editing features, such as content assist, syntax highlighting, unlimited undo and redo, element selection and formatting, and document formatting. Use this dialog to edit the CSS content settings for a CSS file. You can specify CSS profile or restore the default by clicking Restore Defaults.