My best guess is that you are either converting the overlapping text and
image boxes, and they are being converted to an image, which could cause the
shifting. If you are using word wrap, that would create problems. In your
browser go to View > Text size and make sure it is at medium. Do a web
preview, select some text by left clicking and dragging across some text. If
you can't select it, it has been converted to an image.

There are print document formatting techniques that simply do not convert
well to HTML. Run the Design Checker under tools, and see if that gives you
some insights as to what is not working. You may need to back off your
design, one element at a time...just drag it into the scratch area
temporarily...you can move it back later. But after removing each design
element, do a web page preview and see if that fixes the problem. At some
point you will probably have to rework your design to workaround what
doesn't work. Welcome to the joys of web design...

Sorry I can't give you something more definitive.

DavidF