Theme Engine Documentation
How to change <head> content?
ContentAir uses HTML5 standards and UTF8 encoding. They work well in all web development scenarios. You shouldn't need to change these settings.
Some <head> content comes from the page settings (title, description). If you need to add some additional meta tags (e.g. Google Webmaster Tools verification), you can do this under Website settings > Integrations tab.
All needed CSS and JavaScript files are determined and included automatically. You should define all your CSS code in your theme and all JavaScript files in modules. You cannot define them directly in the page header.