forms - Close Button vs Cancel Button

Possible Duplicate:
Save/Cancel/Close button behavior question

I am developing a web application. I have a pop-up with a text field. I am trying to decide how the users can close the pop-up. I currently have two ideas, but am not sure which one is better as I cannot find any research for this.

Users will be using this pop-up text field often as it is one of the main ways of interacting with our project. The pop-up is about 200px wide, 75px tall.

Idea One: Have a cancel button next to the submit button at the bottom of the pop-up.

Idea Two: Have an 'X' button on the top right of the pop-up signifying close the pop-up.