/usr/local/mrtg-2/bin/rateup: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/local/lib/libgd.so.2)

/usr/local/mrtg-2/bin/rateup: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/lib/libgd.so.2)
/usr/local/mrtg-2/bin/rateup: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/lib/libgd.so.2)

/usr/local/mrtg-2/bin/rateup: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/local/lib/libgd.so.2)
/usr/local/mrtg-2/bin/rateup: /usr/local/lib/libpng12.so.0: no version information available (required by /usr/local/lib/libgd.so.2)

vi /etc/crontab
and edit the mrtg line by appending the >/dev/null 2>&1 at the end of line:
*/5 * * * * root /usr/local/mrtg-2/bin/mrtg /var/www/html/mrtg/core/mrtg.cfg >/dev/null 2>&1