The Localize Control lets you localize any element on an .aspx page. It provides a
design time feature not offered by its base class, the Literal control;
in particular, the Localize control provides design time editing of
static content so you can see a default value while working in page
design mode.
You can programmatically manage the text displayed in the control by setting the Text property, inherited from the Literal control.
For more information and example on how to use that control, follow the following MSDN reference:
Localize Class