CSS responsive theme image break layout

[Jack Hard]

I am building this site myspacioclub.com and am using a wordpress responsive theme, and i got this image "bannerfb" with class "banner" that was asked for the customer. So inside the space for the logo i create a new div to put the banner and added this properties to the div of the banner:

.banner { position:relative; top:-170px; left:450px; }

but as the theme is responsive, when i make windows smaller like the size of tablet or cellphone the layout breaks, can someone help me? How could i fix the theme that only use the banner properties when the windows is in a bigger resolution, or any similar solution but the idea is to keep the banner with those properties without been affected by the smaller size.