The "M" in the title is black hidden in a black square in my Firefox browser. Not the greatest first impression for a page about css.

Looks like a good collection of recipes though.

On my Samsung galaxy, with FF the site runs horribly. Scrolling is not smooth at all. Loading takes "long". Is this a me problem?

Same, on mobile Firefox. Chrome renders it okay

Looks like this site is using quite heavy css layout rules. Performance is pretty bad on lower power computers and mobile devices. Not great first impressions.