MSDN Library says:
Remarks
Use the Text property to specify or determine the text contents of the cell. This property is commonly used to programmatically update the contents of a cell.

Note Setting the Text property will clear any other controls contained in the TableCell.
CAUTION This control can be used to display user input, which might include malicious client script. Check any information that is sent from a client for executable script, SQL statements, or other code before displaying it in your application. ASP.NET provides an input request validation feature to block script and HTML in user input. Validation server controls are also provided to assess user input. For more information, see Validation Server Controls.