Preventing Authors from entering pre-formatted text into filtered html field
If you're using the Filtered HTML text format, it should be stripping out spans/divs that contain inline styling. You can double check this at the /admin/config/content/formats/filtered_html path. Make sure the limit HTML tags box is checked and the Allowed HTML tags don't contain any of the HTML elements you're trying to get rid of. 





If you're using the CKEditor (I'm not sure of other editors combined with the WYSIWYG module), you have a few other options to scrub bad markup when it's pasted in. You can check this by editing your Filter HTML profile under /admin/config/content/wysiwyg.

One the toolbar options contains a Paste from Word button, that allows you to paste Word-copied markup into CKEditor. I tend to avoid this myself, but you might find it useful if your users work with many Word documents. 



My prefered option is to use the paste plugin to strip out markup altogether; going this route allows you to restrict your toolbar to HTML elements that will render correctly in both the editor &amp; your theme. You can find this option in paste plugin tab in your WYSIWYG profile page.