Hi Elsa,

The purpose of that box is to ensure that mobile specific pages display properly on mobile devices. Unfortunately, checking it won’t make your page responsive (ie. adapt to both mobile & desktop devices.)

Does that make sense?

We know how important responsive design is though and have some customers alpha testing the feature right now. You can keep an eye on http://inside.unbounce.com for responsive design progress updates and in the mean time, can check out this post which outlines where it’s at in development.

just signed up to unbounce. hows this feature doing? any updates on functionality? 

Hey Henry! Thanks for reaching out :) 

We’ve experienced a ton of upgrades in the last couple of years, one of them being mobile responsive landing pages! Here’s some documentation that can guide you through choosing which templates best suit your needs, all of which offer a mobile responsive design:

http://documentation.unbounce.com/hc/en-us/articles/203788184-Working-With-the-Page-Builder-

If you have any questions along the way, please feel free to reach out in our Community! We’ve got a ton of experts in here who are happy to help 🙂