The table-maker built into the Content Editor is a very useful function. You can drag your mouse across the 8 x 8 grid and quickly create a table. If you need more than 8 rows or 8 columns, click on the Table Wizard button and add as many rows or columns as you need.
In Internet Explorer, when you place your cursor on the edge of the table the cursor will change from an arrow to a 'weather vane.' Right click and it will select the whole table and you can set the Table Properties of the table. The Table Wizard will then appear. For the width you can type in a number and it will fix the width of the table at that number of pixels. Most people find it easier to use percentages, for example 100%, and that will set the width of the table to cover the entire width of the page. You can also set Cell Spacing, Padding, Alignment, and Color as well as choose from a series of pre-configured tables styles from the CSS Class Layout drop-down. When you are done setting you table properties, select OK to apply those changes into the Content Editor.