With that said, there will be certain limitations to certain styles, due to some performance indications. Here are a list of the CSS regulations:
Inline Style Attributes: Styles must be indicated in the header of the page using a custom AMP tag.
!important: It is important that Google AMP be able to enforce its sizing regulations on a webpage, and therefore usage of this is not allowed.
<link rel=“stylesheet”>: This is against policy with the exception of using custom fonts.
* (universal selector): The universal selector is banned as it can evade other selector restrictions.
:not(): This can be used to imitate selectors.
Pseudo-Selectors: These will have certain restrictions in Google AMP. Tag names must not start with amp-.
-amp- and -i-amp- tag names: These tags are reserved for internal use only.
behavior, -moz- binding: This is not supported by Google AMP.
Within Google AMP there are also certain restrictions on HTML tags to ensure Google AMP best practices. AMP has created it’s own set of HTML tags called AMP HTML that replaces some of the limitations of HTML. Examples of restrictions include: