ArminStockner:So do you have an existing section <Membership> in your web.config? Post it shortly.
And where is your database? And does the database exist?
The database works fine and is located on the same computer as the website application. Below is part of the web.config file...
<connectionStrings>
<remove name="LocalSqlServer"/>
<add name="LocalSqlServer" connectionString="Data Source=localhost;Initial Catalog=INVENTORY;workstation id=ASPNET;Integrated Security=True" providerName="System.Data.SqlClient"/>
</connectionStrings>
<system.web>
<identity impersonate="true"/>
<compilation defaultLanguage="vb" debug="true">
<compilers>
<compiler language="vb" type="Microsoft.VisualBasic.VBCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" extension=".VB" compilerOptions="/define:Debug=True /define:Trace=True /imports:Microsoft.VisualBasic,System,System.Collections,System.Configuration,System.Data,System.Drawing,System.Web,System.Web.UI,System.Web.UI.HtmlControls,System.Web.UI.WebControls"/></compilers></compilation>
<customErrors mode="Off" defaultRedirect="errorpage.aspx">
</customErrors>
<authentication mode="Forms" />
<!-- AUTHORIZATION
-->
<membership defaultProvider="SqlProvider" userIsOnlineTimeWindow="15">
<providers>
<clear/>
<add name="SqlProvider" type="System.Web.Security.SqlMembershipProvider" minRequiredPasswordLength="5" minRequiredNonalphanumericCharacters="0" connectionStringName="LocalSqlServer" applicationName="Thornwood" enablePasswordRetrieval="true" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="true" passwordFormat="Encrypted"/>
</providers>
</membership>
<machineKey validationKey='54C80D2111F39CDB41692E097F017FA461E6D8C5E664B50949E1EAEE4B9387E51690BB82B30CA2DDF159637DDA04E94C7D830BD75202C2A7B3B4461A77C9F274' decryptionKey='C48FFDCBF6244851EF1F5F5451AB54337CB9F40B6ECAFEE9' validation='SHA1'/>
<authorization>
<allow users="?"/>
<!-- Allow all users -->
<!-- <allow users="[comma separated list of users]"
roles="[comma separated list of roles]"/>
<deny users="[comma separated list of users]"
roles="[comma separated list of roles]"/>
-->
</authorization>