Register CSS to SP Master Page

http://mosshowto.blogspot.com/2010/06/sharepoint-2010-registering-css.html

http://social.technet.microsoft.com/Forums/en-US/sharepoint2010programming/thread/fc22110f-c83a-48ae-9f18-6a38a672e568/

 protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);
            CssRegistration css = new CssRegistration();
            css.Name=SPContext.Current.Web.Url +"/css/mcstyle.css";
            css.After = "corev4.css";
            this.Controls.Add(css);
        }