Incorporating dynamic content into a website

Your company wants to update its website, which was built using ASP.NET MVC. The website is a portal for independent musicians to upload their recordings. Both registered and unregistered visitors can listen to music and provide feedback and comments. The main layout was done using tables to position elements within the page.

How can a webpage be rendered with dynamic content depending on the type of user?
Some of your potential visitors do not have browsers that support HTML5. How will that affect your design choice?