Upload an Alternate Style Sheet in SharePoint 2010
When do you use the alternate style sheet in SharePoint 2010, and what do you put in it? Use an alternate style sheet if you want to keep the default.master or another predefined master that’s applied, but override certain CSS styles linked to those masters, including the core.css. Another reason you may upload an alternate style sheet is to override control styles or add styles for the HTML Editor Ribbon.
If you know how to make custom themes, you may not need to use an alternate style sheet to change colors and fonts for your site.
Use the tools, Firebug and/or IE Developer Toolbar, to locate a style you want to change. Or you can copy the associated CSS file for the predefined master you want to use (for example, nightandday.css) or the core CSS file (corerev4.css), and modify a copy of those files to upload as your alternate CSS file.
You need to include only the styles you want to override. In fact, you don’t need to override every descriptor. If you only want to override the color, that’s the only descriptor you need to include for the class or element. The site continues to use default styling for the other properties of the element.
You can edit a CSS file using any text editor or an HTML editor, such as Dreamweaver or SharePoint Designer. When you’ve completed your alternate style sheet, save it to the Style library where the other styles are located.
To upload the alternate style file:
Choose Site Actions→All Site Settings.
The Master Page link appears in the Look and Feel section.
Open the Master Page settings by clicking the Master Page link.
The Site Master Page Settings page opens. This page has three sections, Site Master Page, System Master Page, and Alternate CSS URL.
In the Alternate CSS URL section, select the Specify a CSS File to Be Used by This Publishing Site and All Sites That Inherit from It radio button.
The Browse button enables.
Copy/paste the path to your file in the field or click the Browse button to locate where you uploaded your CSS file in the Style library.
If you click the Browse button, make sure you’re in the correct folder by clicking the Style Library link on the left.
Select the file, if you clicked the Browse button, and then click OK.
You return to the Site Master Page Settings page. The path to your alternate style sheet appears next to the Browse button.
(Optional) Select the Reset All Subsites to Inherit This Alternate CSS URL check box.
If you want all the subsites under the site you’re on to use these same alternate styles, select this check box. If you don’t want the child sites to inherit the styles, leave the check box blank.
Your alternate styles appear.
Note your options in the Alternate CSS URL section in case you want to reset them in the future. You can select the Reset to Use the Alternate Style Sheet of the Parent Site check box (if there’s an alternate style sheet) or select the Use Windows SharePoint Services Default Styles radio button.