Copying and pasting from Microsoft Word is a well known problem using any CMS (WordPress, Joomla, etc.). This issue seems to come up a lot so we'll explain it here and give you ways to make sure it does not happen.
Sanitize Formatted Text Before Pasting
When you copy anything (text, tables, images, etc.) from another program, like Microsoft Word for example, and then paste into an editor in your browser, some extra formatting information that Word has embedded comes along. This extra formatting information can often make some strange things happen in the editor because they are different programs and Word's formatting is not pure (or good) HTML.
Copying and pasting from Word works best when you sanitize the text, removing that extra formatting. Here are two ways to do that:
The first method is probably the best way to do it. WordPress has a good system for pasting from Word and so does Joomla.
If you need to copy and paste tables, then please note that you will have to rebuild the entire table again in HTML. Sorry.