error on dotnet 2005 websites

[Emrani]

I already write my codes in dotnet 2003. Recently I moved to dotnet 2005. I
developed some mobile applications that work well. But, when I start to
develop web sites, they don't work. One of errors that is due to calling an
empty asp.net website with only one label is such belowe lines:
Server Error in '/website1' Application.
--------------------------------------------------------------------------------

Configuration Error
Description: An error occurred during the processing of a configuration file
required to service this request. Please review the specific error details
below and modify your configuration file appropriately.

Parser Error Message: Unrecognized configuration section 'connectionStrings'

Source Error:
Line 10: <configuration>
Line 11: <appSettings/>
Line 12: <connectionStrings/>
Line 13: <system.web>
Line 14: <!--
Source File: C:\Documents and Settings\Administrator\My Documents\Visual
Studio 2005\WebSites\WebSite1\web.config Line: 12
--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:1.1.4322.573; ASP.NET
Version:1.1.4322.573
after removing the line connectionstrings, another error refering to
namespaces ocurred.

Is it due to my dotnetfx?