Robert (@zeebe) is right about the theme. Not only for search engines, but the customer experience. More and more users are on mobile devices, and a non responsive theme just doesn’t work on smaller screen sizes.
Both of these should be able to be done with custom CSS, but the code needed might vary depending on what theme you’re using. This is where providing a URL to at least a test page will help the folks trying to help you. Otherwise they have create a test site of their own using the same theme to help you.
That again would probably be better done by choosing a different theme than trying to modify the theme you’re currently using. There’s several different responses themes that come with RapidWeaver, they have different “banner” styles.
There’s also hundreds of addon themes available that might fit the style you’re looking for. Might take a look at themeflood, if none of the included themes suite what you’re looking for. They have a good selection and have demo versions you can try before you buy on all their themes.