table helplines

Hello,

I'm an absolute novice in FCK-Editor, so please by patient in case my question is to simple for an expert
I'm using DotNetNuke 4.9.0 and have an issue with tables within FCK-Editor: on numerous pages we are using tables for displaying information. These tables uses the attribute 'border=0', so no lines will be displayed. I'm sure, FCK-Editor shows helplines (light grey) while entering text in former DNN versions, so users can see, where the different table cells are.

My question is: how can I tell FCK-Editor to show table helplines while entering/editing text?
I'm not familiar with CSS - unfortunatelly. Where can I set this parameter?

Best and thanks in advance

Joerg