Regarding font problems, I have found that even typing the text directly into the Design editor on Auctiva, eBay or Turbolister that font colour and sizes can change for no apparent reason.
So do not edit pasted Word text. I use the ctrl-c & ctrl-v approach, editor asks clean it ?, I say no by cancelling and in it goes. Result is what I want with horrendous looking HTML but seems to load and display ok even with my slow PC.
The design editors build complex and heavy looking HTML and get confused easily and in my experience previewers associated with the above rarely show exactly what you will see when live. Often they have shown font errors in preview which were non-existant when listed. I wasted many hours finding that out !
Another complication is that a good HTML based display will dynamically rearrange the text wrapping to minimise the use of the scroll bar and also resize the text according to the users preference, (the latter is also a cause of previewers distorting font size).
If you are good at using a tool like Frontpage or even writing raw HTML then you could probably write more efficient code. I am not good at HTML and rather sell items than become a HTML expert.
In the end use what posts correctly and stick to it, bit of trial and error, do it before you posts 100's of listings and it all ends in tears as so often gets written on these boards.
