Watch how to fix it on YouTube:

 Some NuGet packages were installed using a target framework different from the current target framework and may need to be reinstalled. Visit http://docs.nuget.org/docs/workflows/reinstalling-packages for more information.  Packages affected: EntityFramework, Microsoft.Net.Http

- in my case I got this error because I changed target framework to .Net 4.0 (from .Net 4.5)
- to fix it - go to
Tools/NuGet Package Manager/NuGet Package Console and execute the following command:
PM> Update-Package -reinstall 

Javascript - how to fix error - Expected hexadecimal digit

Watch this exmaple on YouTube:
Replace:
    Private Sub dispMessage(ByVal message As String)
        Try
            Dim myScript As String = String.Format("<script> alert('{0}');</script>", message)
            Page.ClientScript.RegisterStartupScript(Page.GetType(), "script", myScript)
        Catch ex As Exception
            Response.Write(ex.Message)
        End Try
   
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        dispMessage("Record has been saved\updated.")
    End Sub

With:

    Private Sub dispMessage(ByVal message As String)
        Try
            Dim myScript As String = String.Format("<script> alert('{0}');</script>", message)
            Page.ClientScript.RegisterStartupScript(Page.GetType(), "script", myScript)
        Catch ex As Exception
            Response.Write(ex.Message)
        End Try
   
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        dispMessage("Record has been saved-updated.")
    End Sub

\u - is causing this error