Use a different font. Helvetica Light is not the best choice for screen design. It is fine for print, but not for screens.
Thanks for the reply
But the "publish online" version is also viewed on my screen and looks great??
BTW It's Hypatia, not Helvetica. Hypatia is designed to look good on screen and print.
My question was more about why there is a difference between the two versions, epub3 and via the new "Publish Online" The Publish Online version is the version I really need right now and that's looking good.
Fixed Layout keeps the relation and the optical form of the layout, but not the size as this must be adapted according to the device. You end up in a scaled layout which may cause in a worse readability. For that purpose I never use the same layout as I would do with print, I use larger font sizes. You mast be aware that with smaller devices the pages and the font size become smaller.
Thanks again, Willi
This document was designed from the start as a Digital Publishing document, Print is not a consideration here. The "Publish Online" version looks great when seen on any device. The version from the export to Epub3 does not.
You can try Object Export Options>EPUB and HTML>Preserve Appearance From Layout: Rasterize Container and see how that works.
Very many thanks for those tests, Steve. They convinced me that the cause was in my document.
Visually, I could not see the issue, but when I checked everything connected with the type, I discovered that there was an outline applied to the text. I corrected that and now the text is readable in the epub.
It's very interesting that the Publish Online apparently treats outlined text differently from the way that Epub export treats them.