Hai friend i have read your mesage,
to use connectionstring in web.config..
 <configuration>
    <connectionStrings>
        <add connectionString="Server=server name;Database=databasename;uid=user id;pwd=password;" name="ConStr"/>
    </connectionStrings>  
</configuration>

To call the connection string to our page
SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ConStr"].ToString());     
I think it may useful to you..
If still you have doubt reply me.   

visit this link for further clarification 

 http://foraspdotnetdevelopers.blogspot.com/