Hi Raju, 

1. here is my Page2.xaml:

UserControl x:Class="SilverlightTest2.Page2" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:fromInternet="clr-namespace:SilverlightTest2;assembly=" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d"

i omit the assembly name because i couldn't find it though i tried right click on Solution and Click on Properties item

2. after this declaration the intelisens found alone that CaptchaControl is one of the files in the "fromInternet" xmlns, and i added this line to my Page2.xaml:

but i have get an error:Error 1 Unknown namespace clr-namespace:SilverlightTest2;assembly=. [Line: 102 Position: 66] E:\SilverlightTest2\SilverlightTest2\Page2.xaml  

and i also get a warning: Warning 2 The tag 'CaptchaControl' does not exist in XML namespace 'clr-namespace:SilverlightTest2;assembly='. E:\SilverlightTest2\SilverlightTest2\Page2.xaml

thanks a lot

yosi