HTTP stands for Hyper Text Transfer Protocol. It is used to publish Web pages. The web pages are commonly written in the HTML (Hyper Text Markup Language).
The policy on content is included in general terms. You can find it at https://www.host.sk/terms.php.
By registration, you gain space at host.sk's web server. All you need is to upload your page to this space. More information about how to upload your web page you can find at FTP FAQ section.
Except HTML, you can use one of the scripting languages. You can use any scripting language that is processed at a client side or PHP, the scripting language processed at the server side. PHP is a C based programming language. It allows you to cooperate with databases, too.