With ‘OK’ button, ‘Cancel’ should appear as secondary button or link?

When I make web application designs, every time I style form or overlay boxes with OK and Cancel button. I think of making them different. But is it a good practice?

Some people recommend primary and secondary buttons but I dont feel 'cancel' is so important to give it a secondary button status, what if the application doesnt have enough secondary buttons, I dont want to create and use a secondary button only for 'Cancel'.