Any text that you see is in a language file ...

When you are unsure where that might be, use the Tools ... Developer's Tool Kit ...

In the bottom input box, enter a part of what you are looking for such as:
have you seen

Select the Catalog ... and click Search ...

This will find for you where this text is located ... usually this will be in a constant or constants where you can change it to what you would rather see ...

NOTE: always use the templates and overrides for your changes rather than change the original files so that you do not wipe out your changes when you do upgrades ...