Custom Login page CSS and master page on WSS 3.0 Forms Authentication.

1. Go to "C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS" on your WSS Server.
   
2. Copy login.aspx and simple.master files there and rename them (I gave MyComp_Login.aspx and MyComp_simple.master).
3. Copy \12\TEMPLATE\THEMES Folder to Layout folder and change its name suitable for your application.
   
4. Open your custom master file (For my application "MyComp_simple.master") with Visual Studio (I opened with VS 2008) add HTML link tag to your custom.css(link rel="stylesheet" type="text/css" href="/_layouts/My_Themes/MyCompTheme/theme.css") just below <Sharepoint:CssLink tag and save changes.
   
5. Open MyComp_Login.aspx and replace value of MasterPageFile = "/_layouts/MyComp_simple.master".
6. Now open your web.config from "c:\Inetpub\wwwroot\wss\VirtualDirectories\PORT_Number"
7. Find "/_layouts/login.aspx"
   
   
8. Replace with "/_layouts/MyComp_login.aspx"
   
   AND Save changes.
9. Resest IIS, Clear Private data and History from browser and open your application from new instance of browser.
10. Hope you will make it as me...;)
    

--NH