Can HTML and CSS files include backdoor/ trojans ?

I download templates HTML/CSS templates from the internet.
I just want to know , can they include backdoor/trojans ?

thanks

 

Any downloaded file can contain such things but HTML cannot. I once read about how a CSS file COULD contain such a thing using the 'content' attribute of some properties but don't recall what the issue was or if browsers have fixed that.

It's also possible for the downloaded markup to have javascript mixed in with it and, if you opened that page, could execute some malicious code.

 

Thanks for answer.
Take care