By default, all of the RadTextBox control displays a blank input area when the value has not been set:
You can change this default appearance when the input control does not have focus to display any string you like. Set the string you want to display as the value of the EmptyMessage property. When the input control does not have focus, it displays the string you have set:
Once you have set the EmptyMessage property to a non-empty string, you can use the EmptyMessageStyle property to change the display properties of the input control when the empty message is showing:
The DisplayText property can be used if you do server-side validation and you want to inform the user that their value is not valid after the PostBack.
The following specifications will be helpful when operating with RadInput display properties:
The empty message does not need to be a valid value for the input control. For example, you can use a string of text as the EmptyMessage property of a RadNumericTextBox, RadDateInput,or RadMaskedTextBox control.
RadTextBox is unable to show a readable EmptyMessage or DisplayText when its TextMode is set to Password mode. Instead, the regarding message is displayed with bullets.In this case you could use a Label as an alternative for EmptyMessage:
How to Use an EmptyMessage with Password RadTextBoxes
Set EmptyMessage for TextBox in Password Mode