HTMLDOC Problem:

Htmldoc produced no pdf-output.
Commandline:

/usr/bin/htmldoc -t pdf13  --webpage -f /www/htdocs/v082500/typo3temp/hd_LO56tM - 2>/www/htdocs/v082500/typo3temp/se_06tcye

This is the (stderr) output of the htmldoc command without the htmldoc_append parameters:
If you see no errors here please check your htmldoc_append parameters too.

HTMLDOC(22459) INFO: HTMLDOC 1.8.25 starting in CGI mode.
HTMLDOC(22459) INFO: TMPDIR is "(null)"
Can't open display: