So, the revised, slightly cleaner code looks like this:

(with-open-file (ifile "key.html" :direction :input)
  (let ((nlines 0))
    (loop
       while (read-line ifile nil nil)
       do (incf nlines)
       finally (return nlines))))

The even more compact version uses the for and from loop functionality:

(with-open-file (ifile "key.html" :direction :input)
  (loop
    for nlines from 0
    while (read-line ifile nil nil)
    finally (return nlines)))

Thom

[1] I learned my Lisp somewhat in a vacuum, so I sometimes find that
what I consider elegant or clean, other people consider ugly or unclear.