Using the Extensible Stylesheet Language Transformations (XSLT) coding language, XSLT style sheets take the raw XML data of an RSS feed and convert it into branded and highly formatted HTML.
While CSS files are managed from Reports and Tools, XSLT style sheets are managed independently. If you use XSLT, make sure you create at least one style sheet for each available format: RSS 2.0, RSS 1.0, and ATOM. For example, if you plan to create ATOM RSS feed links, make sure you have an XSLT style sheet coded specifically to handle the ATOM format.
If you are not comfortable working with XSLT, online services such as FeedBurner will transform your RSS link into a highly stylized and customized HTML view. These services are gaining in popularity as a new marketing channel, and for organizations who wish to fine-tune their RSS feeds or access basic tracking metrics.