Copy `scribble/sigplan`'s style file to `scribble/lncs` because the HTML renderer expects to find an `lncs.css` file.
The path is changed to ftp://ftp.springernature.com/cs-proceeding/llncs/llncs2e.zip which is the official file listed at http://www.springer.com/us/computer-science/lncs/conference-proceedings-guidelines