How to integrate css in email template? I tried and got this error:
CSS inlining error: DOMXPath::query(): Invalid expression in selector 100% in E:\xampp\htdocs\newmetal\vendor\pelago\emogrifier\Classes\Emogrifier.php on line 372
It looks like there's an issue with your CSS. Magento 2 doesn't support certain selectors for emails. You should review your CSS for any errors and check that you're not using any unsupported selectors.
Unsupported selectors (examples in parenthesis): * first-child (div:first-child) * last-child (div:last-child) * nth-child (div:nth-child(3n+1)) * universal (*) * pseudo (a:hover, a:active, a:focus, span:before, span:after, etc)
Here's a more detailed answer explaining the issue: https://magento.stackexchange.com/a/132691/50223