<![CDATA[<%@ Register TagPrefix="FTB" Namespace="FreeTextBoxControls" Assembly="FreeTextBox" %>]]>
In Source,-
<FTB:FreeTextBox ID="txtContent" runat="Server" ToolbarLayout="ParagraphMenu, FontFacesMenu, FontSizesMenu |FontForeColorsMenu, FontForeColorPicker, FontBackColorsMenu |
Bold, Italic, Underline, Strikethrough|
Superscript, Subscript, InsertImageFromGallery, CreateLink, Unlink,
RemoveFormat, JustifyLeft, JustifyRight, JustifyCenter, JustifyFull, BulletedList,
NumberedList, Indent, Outdent| Cut, Copy, Paste, Delete, Undo, Redo, Print, Save,
ieSpellCheck, StyleMenu| SymbolsMenu, InsertHtmlMenu, InsertRule, InsertDate,
InsertTime, WordClean, InsertImage, InsertTable,
InsertTableRowAfter, InsertForm,InsertImageFromGallery" Height="200px"
Width="350px" ImageGalleryUrl="ftb.imagegallery.aspx?rif={0}&cif={0}" />
Before that You have to Download FreeTextBox.dll . And
In Code behind you can do coding like textbox using txtContent.Text
Hope this can Help You.