Hi there bnLauren! :)
Your problem can be solved with some simple css. You need to define a width for the panel-grid based on the user's screen size and then set the margin left and right to auto.
Try this css:
@media only screen and (min-width: 1200px){ #pg-4-1, #pg-4-2 { width: 1170px;
}
}
@media only screen and (min-width: 992){ #pg-4-1, #pg-4-2 { width: 970px;
}
}
@media (min-width: 768px)
#pg-4-1, #pg-4-2 { width: 750px;
}
@media only screen and (min-width: 768px){ #pg-4-1, #pg-4-2 { width: 750px;
}
}
#pg-4-1, #pg-4-2 { margin-right: auto; margin-left: auto;
}
If you don't know how to apply css to your website, read this article: http://touchcoding.net/how-to-apply-custom-css/
Hope this helps you out :D