In case you have a VGA external port that doesn't support EDID and can't set your external monitor to a high enough resolution I added to Hanynowsky's workaround at http://askubuntu.com/questions/119843/how-to-force-multiple-monitors-correct-resolutions-for-lightdm.
In case you have a VGA external port that doesn't support EDID and can't set your external monitor to a high enough resolution I added to Hanynowsky's workaround at http:// askubuntu. com/questions/ 119843/ how-to- force-multiple- monitors- correct- resolutions- for-lightdm.