On mobile you should never use absolute values for width, unfortunatelly I am not able to provide support on custom development and css instructions. I recommend to check on google css and responsive design.
<div style="float: none; margin: 0 auto; width: 728px; text-align: center; ">
<div style="float: none; margin: 0 auto; width:100%;max-width: 728px;min-height:100px; text-align: center; ">
@angelaI do not think it is for mobile, but for tablets at least.For mobiles code should be something like:Code: [Select]<div style="float: none; margin: 0 auto; width:100%;max-width: 728px;min-height:100px; text-align: center; ">Theme can also change some stylings so it is required to check block via console.