If there is strange formatting (eg weird fonts and spacing) then it is likely that content was copy and pasted in Visual mode instead of Text mode

To check

1. Click on Text tab
2. You will see lots of strange code everywhere (particularly <h1>, <h2>, <p class=..> and <p>'s

To fix

1. In Visual mode
2. Select and Cut all the text (to remove it)
3. In Tab mode
4. Paste
5. Then go back to Visual mode and format the text correctly