Is there a way to change the message that comes up when you don't answer a mandatory question? We want it to say something like "Please answer this question." I imagine there has to be a javascript solution for the template.

You need to adapt this text in the translation file. Please note that these changes get easily overwritten when there is an update for the translation.

Thanks holch! I am a little confused by the final step (within the link you included). What does it mean to do this?

Place the particular .mo file in the right language folder in /locale by replacing the existing one - for example for French this would be /locale/fr/LC_MESSAGES/fr.po

From what I understand you need to create a .po file and a .mo file and they both need to be placed in the folder for the respective language. This folder you should find in the locale folder in your limesurvey installation.