I wonder why, after posting by C&P from MS Word I saw HTML codes.
Also, why clicking on font size doesn't change my font?

This portion was posted after C&P from Word

If you want to copy & paste from Word into a post, then you'll need to switch from the WYSIWYG editor to the Standard editor. You can do this on a per-post basis by hitting the "Switch Editor Mode" toggle button (http://forums.johnstonefitness.com/plasma/editor/switchmode.gif) at the top right-hand side of the new post dialog box. Do this before pasting.

You can permanently switch to the Standard editor in your Control Panel options (http://forums.johnstonefitness.com/profile.php?do=editoptions). The setting is under the "Miscellaneous Option" section.