I have looked at your screenshot after expanding it but it is still too small to see the problem.
Please take a full size shot and post that. In the thread it will show it reduced but clicking on it will then enable us to see it full size.
Please see the sticky topic Before You Post and always start threads with the version of RoboHelp being used.
Also have you tried a different skin? Is the problem still there?
See www.grainge.org for RoboHelp and Authoring tips
You have to do that in whskin_frmset010.htm, by changing the frame border.
If I'm not mistaken, the steps to do that are listed in Rick's Skinny on
If it's not there, let me know and I will post some instructions.