Adding alternative text tags to images in Microsoft Word 2007 documents makes them accessible to screen-readers and users with disabilities.
To add alternative tags to images in Microsoft Word 2007, click the picture that you inserted.
The Picture Tools tab appears.
Click Format.
Click the arrow in the lower-right corner of the Size group.
The Size dialog box opens. Click the Alt Text tab.
In the Alternative text box, type the alternative text, and then click Close.