Well, both languages have same sound in order to understand their syntax, style, attribute and tags. HTML stands for Hyper Text Markup Language while Cascading Style Sheets is known as CSS.
Before choosing HTML or CSS, one should know their specific work. So, let's begin with HTML use. Generally, HTML is used for making a structure of web page which is going to appear on World Wide Web (WWW). Whereas, CSS is used to design the web page through its layout, font style, color manner. Particularly, CSS makes good presentation of website to look better.
Now back to initial question that which language should be preferred in the beginning of programming languages. So, my recommendation would be with HYML because concept of HTML is easy to understand in the beginning and even it helps to make people understand the basic & common difference between HTML and CSS. There are plenty of things to know about HTML and CSS, but when stating is from HTML then there is something else.
Many coaching and institute of computers or programming languages choose HTML as first priority than CSS when web designing is being taught to students. Almost every teacher or trainer follow the same pattern to teach students web designing.
Anyhow, it will be your decision that what to choose first but if you wish to learn it and about to join an institute so, I would say you to select the best one. Here, you can find a best institute of programming languages.