When you save a document in Microsoft Word 6.0/95 format or when the Disable features introduced after check box is selected (Tools menu, Options command, Save tab), Word makes unsupported options unavailable. Choosing to disable these options makes it easier for you to create documents that appear correctly in Word 6.0/95.
To make all Word options available again, clear the Disable features introduced after check box or save your document as a Word 2002 document by clicking Word Document in the Save as type box, (File menu, Save As command).