Are templates designed using HTML?
HTML is not used to design Wiki pages and templates. Confluence uses a language called Wiki Markup, which is based on Textile. If you click on this link you will get an overview of what Textile does. There is also a section in the Confluence Documentation 2.10 that you may find helpful. It explains how to add a template and it shows you some examples of Confluence Markup and how it would look using HTML. You need to be a space administrator to create a space template.