Calling stylesheets within a plugin
Controlling how your plugin's output looks onscreen (whether in the WordPress Dashboard or on the front end of the Web site or blog) is best controlled through a stylesheet. If you've been around Web design and HTML, you're probably familiar with CSS (Cascading Style Sheets). Nearly every styling aspect for a Web site is controlled by a stylesheet, and WordPress is no exception. If you want to read the authoritative guide to stylesheets, visit the W3C.org Web site at http://www.w3.org/Style/CSS. (For more on CSS, see Book VI.)
You can use a single stylesheet to control how your Plugin Options page looks in the Dashboard, how your plugin widget looks in the Dashboard, or how your plugin displays information on the front-end Web site.
Create and use a separate stylesheet for the plugin within the Dashboard and the plugin's display on the front end because the stylesheets are called at different times. The back-end stylesheet is called ...