The 10th file isn't an image; it's an HTML Cascading Style Sheets (CSS) file named OWAColors.css. OWA uses the CSS only for color specifications. When you open the file, you'll see groups of lines that specify colors for specific CSS styles. For example, the CSS lines that Figure 2 shows specify that any element whose style is set to cbToolbar will use the background image from the /exchweb/themes/0/tool-bkgd.gif URL and that the image's bottom border and background will have the specified colors. In the CSS, you specify colors by using a standard Red-Green-Blue (RGB) color specifier. Each color component has a value from 0 to 255 in hexadecimal format, with a pound (#) character prefix. The value #000000 specifies black, #FFFFFF specifies white, and other colors correspond to intermediate values between those two extremes.
By editing the colors specified for various elements, you can customize the elements' appearance. Although adjusting all the colors to look just right requires patience, the task doesn't take long. If you know a skilled Web designer, he or she can probably speed the process by suggesting pleasing color combinations.
No matter what colors you assign, you should know that the public-folder interface won't honor them if the public-folder server is running Exchange 2000. In addition, if public folders are configured for anonymous access, the public-folder server won't be able to determine which user is reading the folder and thus which theme to display.
Making Themes Available
After you create a theme, you need to register it so that your Exchange mailbox server knows that the theme exists. You register themes on your organization's Exchange mailbox servers and put the theme files on all OWA machines, including all front-end servers.
To register a theme, create a REG_SZ registry value for the theme under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeWeb\OWA\Themes subkey. Specify the name of the theme as you want it to appear in OWA's Options pane. In the value's contents, you specify a set of four name and value pairs, all of which are mandatory. (If you omit a pair, OWA will ignore the entire theme.) The pairs are
- Id—the theme ID, which you can specify in decimal or hex format. The theme ID can't conflict with an existing theme ID and must be no larger than 0x80000000 (in other words, you must not set the pair's first bit).
- Path—the path relative to the exchweb\themes directory that specifies the location of the theme files.
- Title—the theme name, which must be less than 512 characters. Whatever you put here will appear in the OWA Options pane as an available theme.
- Bgcolor—an RGB specifier for the theme's background color. For example, the following value specifies theme ID 200 (in hex format):
Id=0x200;path=3sharptheme;
title=3sharp;bgcolor=#FFFFFF
This theme uses a white background and resides in the exchweb\themes\3sharp directory.
User Selection
Users can select a theme by clicking the Options button at the bottom of the OWA navigation bar and choosing a theme from the Appearance section. By default, the Options button lists the themes that ship with OWA: Default (blue), Olive Green, Silver, Burgundy, and Dark Blue. If you want to force users to use a particular theme, create a new REG_DWORD registry value named DefaultTheme under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeWeb\OWA\Themes subkey and specify the theme ID that you want users to use. The specified theme will appear for all users. However, users can change the theme manually, if they choose.
Tailor-Made OWA
You can use themes to skin OWA now and modify the most important aspects of its appearance. Combine skinning with segmentation (i.e., the ability to selectively enable OWA features), and you can deliver to your users the particular look and features you want them to have. (For information about OWA's segmentation settings, see "Customizing OWA 2000 Access," June 2002, http://www.winnetmag.com/microsoftexchangeoutlook, InstantDoc ID 24778.)