I'm looking for an application/tool to easily create a mock GUI. This GUI will be used by users to control home devices remotely. They can login to a website or use an application to view/control devices. The GUI should look good, but nothing very fancy. It should have checkboxes, lists, radio buttons etc.
The important thing is that since this is just a mock, it should be quick to prepare. While I am a programmer and know C, Python, I would prefer something where I can just drag and drop elements and make a website GUI rather than code.
The software/tool must be free or very cheap. I thought of Dreamweaver, but it's expensive and I guess I'd need a small learning curve (CSS, HTML..)
What should I choose?