remain always in mobile device size.

Hi Daniel!

I have two question please check them:
1, Is your template responsive?
2, Did you enabled the Responsive mode with down-scale? (Slider -> Responsive mode -> Down scale) Here is the documentation for it: http://www.nextendweb.com/wiki/smart-slider-documentation/slider-settings/

All in all I think the best if you send me an email which contains the URL of your site, then I can see your site and help for you! Here is my email address: daniel@nextendweb.com

Have a great day Daniel and I look forward to hearing from you! 🙂