Show different banners on mobile CSS

Hello guys,

It has been a while.... Hope to find you all in good health.

On one of our domains called bettinggroups.com we just added some i-frame banners. All looking great. Except we would love to show a different size and style on mobile divices.

Sow how to have 2 i-frames on the page.. one olny showing on desktop.. The other only showing on mobile. Could we CSS this?

Example:

Mobile:
<iframe scrolling='no' frameBorder='0' style='padding:0px; margin:0px; border:0px;border-style:none;border-style:none;' width='300' height='250' src="" ></iframe>

Desktop:
<iframe scrolling='no' frameBorder='0' style='padding:0px; margin:0px; border:0px;border-style:none;border-style:none;' width='970' height='250' src="" ></iframe>