An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Data.SqlClient.SqlException: An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Source Error: 

here is my web.config file:
<?xml version="1.0"?><!-- 
Note: As an alternative to hand editing this file you can use the 
web admin tool to configure settings for your application. Use
the Website->Asp.Net Configuration option in Visual Studio.
A full list of settings and comments can be found in 
machine.config.comments usually located in 
\Windows\Microsoft.Net\Framework\v2.x\Config 
-->
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0"> 
<appSettings>
<add key="EmailFrom" value="webmaster@reaganpower.com"/> 
<add key="EmailSubject" value="File Ready for Download!"/>
<add key="SmtpServer" value=""/> 
<add key="MailUser" value=""/>
<add key="MailPassword" value=""/> 
<add key="MailPort" value="25"/>
<add key="EmailFormatSelected" value="Text"/> 
<add key="PageTitle" value="Send It Now!"/>
<add key="ShareLocalFolderPath" value="H:\MIS Department\Intranet\SendItNow\FileStorage\"/> 
<add key="httpDownloadPath" value="http://misfs/SendItNow/ContentFiles/"/>

<!--
<add key="CurrentTheme" value="CleanBlue" />--> 
<add key="CurrentTheme" value="CleanOrange"/>
</appSettings> 
<connectionStrings>

<add name="ConnectionString" connectionString="Data Source=(local)\SqlExpress;AttachDbFilename=|DataDirectory|\FileShareDB.mdf;Integrated Security=True;User Instance=True"
providerName="System.Data.SqlClient"/> 
</connectionStrings>
<system.web><!-- 
Set compilation debug="true" to insert debugging 
symbols into the compiled page. Because this 
affects performance, set this value to true only 
during development.
Visual Basic options:
Set strict="true" to disallow all data type conversions 
where data loss can occur. 
Set explicit="true" to force declaration of all variables.--> 
 
<identity impersonate="false"/> 
<roleManager enabled="true"/>
<compilation debug="true" strict="false" explicit="true"> 
<assemblies>
<add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/></assemblies></compilation> 
<pages>
<namespaces> 
<clear/>
<add namespace="System"/> 
<add namespace="System.Collections"/>
<add namespace="System.Collections.Specialized"/> 
<add namespace="System.Configuration"/>
<add namespace="System.Text"/> 
<add namespace="System.Text.RegularExpressions"/>
<add namespace="System.Web"/> 
<add namespace="System.Web.Caching"/>
<add namespace="System.Web.SessionState"/> 
<add namespace="System.Web.Security"/>
<add namespace="System.Web.Profile"/> 
<add namespace="System.Web.UI"/>
<add namespace="System.Web.UI.WebControls"/> 
<add namespace="System.Web.UI.WebControls.WebParts"/>
<add namespace="System.Web.UI.HtmlControls"/> 
</namespaces>
</pages> 
<!--
The <authentication> section enables configuration 
of the security authentication mode used by 
ASP.NET to identify an incoming user. --> 
<authentication mode="Forms"/>

<!--
The <customErrors> section enables configuration 
of what to do if/when an unhandled error occurs 
during the execution of a request. Specifically, 
it enables developers to configure html error pages 
to be displayed in place of a error stack trace.
<customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
<error statusCode="403" redirect="NoAccess.htm" />
<error statusCode="404" redirect="FileNotFound.htm" />
</customErrors>--> 
</system.web>

</configuration>

Check out this page:
http://www.datamasker.com/SSE2005_NetworkCfg.htm
David Wier
MCP/ASPInsider
ASPNet101.com - where to look first!
Control Grouper - easily control properties for multiple controls with one control!
Calendar Express - The Best HTML Calendar Generator on the web!
(Please 'Mark as Answer' when it applies)

You need to check with whoever manages the server for connection details to an available SQL Server.  Also, the Full version does not support AttachDbFileName, so they will have to manually attach the db to the server instance.
 
Regards Mike 
[MVP - ASP/ASP.NET]
My site