Cascading Style Sheet usage is very common in SharePoint. Almost every thing in SharePoint UI is styled by CSS. So to customize your SharePoint sites you have to know which style rules SharePoint use. You don’t have to be a CSS Guru but you have to know the basics.
SharePoint 2007 had a single large CSS file named as core.css. If you did any customization on SharePoint 2007, you were probably worked with core.css file. That single file has nearly 5.000 lines of style rules and it is loaded for every page.
In SharePoint 2010 that file is splitted into several smaller CSS files. In that case only the necessary CSS files are loaded on page loads according to the controls that are used in the pages. “core.css” file resides in SharePoint 2010 with the name “corev4.css”. However the style rules are splitted in many CSS files, the core file, “corev4.css” contains almost 8.000 lines of rules. Another heavy CSS file in SharePoint 2010 is “search.css” which has nearly 3.000 lines. These two files make 10.000 lines of style rules which is a huge number for styling.
Fortunately you don’t have to learn these thousands of CSS rules. Heather Solomon, who calls herself as a graphic designer and a SharePoint geek, is publishing SharePoint CSS charts that unleashes the major style rules used in SharePoint. For now there are two versions of these styles charts.