I want develop my first template html.
Have I to follow some guidelines? If the answer is yes, can you link me?
There’s no official guidelines for HTML templates
Just use best practice and common sense, make sure the code is clean and site is optimized etc.
Clean coding needed. But above all the design should be high quality and unique. If the design is not good enough, then clean coded html will also be hard rejected. You can see some popular items of themeforest to understand more.
Last one question.
Exists any api for insert the style switcher?
where can i see it?