A family of Microsoft word processing software products for creating web, email, and print documents.
To quickly resize a table which is "too wide," use the Table Tools Layout tab | AutoFit | AutoFit Window. (To make sure column widths stay fixed, afterwards you may want to click Table Tools Layout | AutoFit | Fixed Column Width.)
Also, note that, by default, Word adjusts for cell margins when placing the table borders/edges. You can set the left and right cell margins to zero for a given table.
[Edit: corrected a typo]