www.wysiwygwebbuilder.com

When I center my page horizontally, it looks just fine in the editor, but when I preview or publish it, there is a big gap between the header and the rest of the page. The header comes from a master page but it didn't help to remove it.

To be able to help you, I need a DEMO project (.wbs file) so I can see all your settings.

I do not need the complete project because that will only take more time to figure out what you have done.
Basically, I just need a small project with one page and object(s) that are relevant to your question.

For further details about how to share a project file, please see this FAQ:
https://www.wysiwygwebbuilder.com/forum ... 10&t=82134

I found the problem!
When I changed the header on the master page from floating to fixed, the gap disappeared.
Anyway the rule of Wysiwyg is broken, since the page looked different in the editor than it looked on the published page, before I did the change!

Without seeing a demo project of your original issue it's hard to say anything meaningful about this. However, you also need to know the difference between fixed and floating. Floating objects stack one after another with other floating objects where a fixed object is taken out of the floating arrangement and fixes to the top of the page and not part of the other objects on the page. This causes the floating objects to 'go under' the fixed heading.

I do not want to criticize this wonderful tool. My mistake that the header was floating. Do not now how that happened. My point is that a perfect wysiwyg tool should take into account the settings in editor mode. However, I have never seen a webtool fixing that, so if Wysiwyg Builder could do that, it would be amazing. Probably too much work though to be motivated.