From DoomWiki.org

Note: After saving, you may have to bypass your browser's cache to see the changes. Mozilla / Firefox / Safari: hold down Shift while clicking Reload, or press Ctrl-Shift-R (Cmd-Shift-R on Apple Mac); IE: hold Ctrl while clicking Refresh, or press Ctrl-F5; Konqueror: simply click the Reload button, or press F5; Opera users may need to completely clear their cache in Tools→Preferences.

body {
font-family: Arial;
}
textarea {
background-color: #000000;
color: #ffffff;
font-family: Verdana Ref;
scrollbar-face-color: #000000;
scrollbar-shadow-color: #666666;
scrollbar-3dlight-color: #cccccc;
scrollbar-arrow-color: #ffffff;
scrollbar-base-color: #000000;
scrollbar-track-color: #000000;
scrollbar-darkshadow-color: #333333;
scrollbar-highlight-color: #999999;
}