Puedes usar la siguiente configuración de la página:
<%@ Assembly Name="Microsoft.SharePoint.IdentityModel, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Assembly Name="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Page Language="C#" Inherits="Microsoft.SharePoint.IdentityModel.Pages.FormsSignInPage" %>
<%@ Import Namespace="Microsoft.SharePoint.WebControls" %>
<%@ Register TagPrefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls"
Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register TagPrefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Import Namespace="Microsoft.SharePoint" %>
<%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
Para poder personalizar el master.page que la pagina va usar debemos agregar el siguiente código en la misma página.
<script runat="server">
protected void Page_PreInit(object sender, EventArgs e)
{
this.MasterPageFile = "~/_catalogs/masterpage/Login.master";
}
<script>
Y para el cuerpo se puede usar la siguiente código:
<asp:content id="ContentInterno" runat="server" contentplaceholderid="PlaceHolderMain">
<div style="display: none">
<SharePoint:EncodedLiteral runat="server" EncodeMethod="HtmlEncode" ID="ClaimsFormsPageTitle" />
<SharePoint:EncodedLiteral runat="server" EncodeMethod="HtmlEncode" ID="ClaimsFormsPageTitleInTitleArea" />
</div>
<asp:Login ID="signInControl" FailureText="<%$Resources:wss,login_pageFailureText%>"
OnLoginError="OnLoginError" OnLoggedIn="OnLoggedIn"
runat="server">
<LayoutTemplate>
<label class="form-label">Usuario:<asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName"
Text="*"></asp:RequiredFieldValidator></label>
<asp:TextBox class="form-input" ID="UserName" runat="server"></asp:TextBox>
<label class="form-label">Clave: <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password"
Text="*"></asp:RequiredFieldValidator></label>
<asp:TextBox class="form-input" ID="Password" runat="server" TextMode="Password"></asp:TextBox>
<label class="form-label-error">
<asp:Literal id="ltlMensaje" runat="server"></asp:Literal>
<asp:Literal id="FailureText" runat="server" Visible="false"></asp:Literal>
<asp:ValidationSummary id="vs" runat="server"></asp:ValidationSummary>
</label>
<asp:button class="form-submit" id="Login" CommandName="Login" runat="server" Text="">
</asp:button>
</LayoutTemplate>
</asp:Login>
<div id="SslWarning" style="color: red; display: none">
<SharePoint:EncodedLiteral runat="server" EncodeMethod="HtmlEncode" ID="ClaimsFormsPageMessage" />
</div>
</asp:content>
Espero que estos pasos les pueda ayudar a configurar una página personalizada en sharepoint
