Hi Phill242. Welcome to the forums.
There are various options, such as adding in extra styles for mobile devices, as PromptSpace said. But that can be unwieldy, especially for large, established sites. Another option is to build a new, mobile-friendly version of your site and redirect mobile devices thither. That could be expensive, though. As a fall back, there are some sites that provide tools for you to knock up your own mobile version of your site that is targeted to mobile devices. This might be a good option for you, at least in the short term, if you want to save time and money. A few examples are: