System.Net.Mail.SmtpException:
The operation has timed out. at System.Net.Mail.SmtpClient.Send (MailMessage message)

Solution :

Sys.WebForms.PageRequestManagerTimeoutException: The server request timed out.

Solution :

Failed to send mail : that domain isnt in my list of allowed rctphosts

Solution :

'Theme' is not a member of 'ASP.Default_aspx'
Solution :

Email error : mailbox not found

Server Application Unavailable
The web application you are attempting to access on this web server is currently unavailable. Please hit the "Refresh" button in your web browser to retry your request.

Failed to access IIS metabase. Exception Details: System.Web.Hosting.HostingEnvironmentException: Failed to access IIS metabase. The process account used to run ASP.NET must have read access to the IIS metabase (e.g. IIS://servername/W3SVC). For information on modifying metabase permissions, please see http://support.microsoft.com/?kbid=267904.
Solution : this error can mean one thing.. u installed iis after installing .net.
cmd>C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Aspnet_regiis –i

Unable to start debugging on the web server. This project is using a website that is configured to use a specific IP address. Specify he machine name in the project URL. Please see Help for assistance.

Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application.

A transport-level error has occurred when sending the request to the server. (provider: Named Pipes Provider, error: 0 - The pipe is being closed.)
Error when ..
Solution:

Invalid postback or callback argument. Event validation is enabled using in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
Error when .. clicked on logout in admin home page
Solution:

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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Error on Conn.Open()

Value of type 'System.Web.UI.WebControls.TableRow' cannot be converted to 'System.Web.UI.HtmlControls.HtmlTableRow'.
Get this eror when dynamically adding a row to a tableSolution:

Concurrency violation: the UpdateCommand affected 0 of the expected 1 records.
U get this error when using update on a dataset … if the command fails
Solution :

Control 'ctl00_ContentPlaceHolder1_gv' of type 'GridView' must be placed inside a form tag with runat=server.
Z code
Response.Clear()
Response.AddHeader("Content-Disposition", "inline;filename=Backup.xls")
Response.Charset = "iso-8859-1,windows-1252"
Response.Cache.SetCacheability(HttpCacheability.NoCache)
Response.ContentEncoding = System.Text.Encoding.UTF7
Response.ContentType = "application/vnd.ms-excel"
Page.EnableViewState = False
Dim strwrite As New System.IO.StringWriter
Dim htmwrire As New System.Web.UI.HtmlTextWriter(strwrite)
'gv.Columns(0).Visible = "False"
GridView1.RenderControl(htmwrire)
Response.Write(strwrite.ToString())
Response.End()

Z Method to include on the page

Public Overrides Sub VerifyRenderingInServerForm(ByVal control As System.Web.UI.Control)
End Sub

Z code to be added in Page directive

<%@ Page EnableEventValidation="false" %>

invalid uri: the format of the uri could not be determined