To give you a short answer: Yes, it is possible, you do not need neither to know HTML nor PHP to be able to create a professionally looking website using the MarbleHost online tools.
To give you better idea what can you expect: To create a website without the knowledge of HTML and PHP you need a content management system installed in your web hosting account. If you are a beginner it may sound like a difficult task (well, for many newbies may be a little difficult) but fortunately MarbleHost has a tool which can do it for you automatically. There are multiple content management systems (CMS) which can you use for this purpose. I recommend to use WordPress because it is the most popular one and you can choose from thousands of free designs.
You can install WordPress automatically from the MarbleHost control panel (you will get access to the control panel after the signup). When installed you will be provided with a link to the WordPress administration where you can setup the design of your website and add content (text, images, videos…).
If you want to know more about WordPress, check out this page: http://www.marblehost.com/wordpress.php