When you are editing your email newsletter message, you can view the properties of your table by right-clicking within the boundaries of the table and choose the Table Properties menu item.
By default, the table properties use a width that has a percentage value. This percentage is based on the viewable area of the screen where the table is displayed. If you do not want to use a percentage value you can change the width to pixels and enter a specific value, such as 800, for example.
Percentage values are good for scaling the content to fit different sized screens; however, they sometimes may render in strange ways if someone is using an unusual screen resolution. Very high screen resolutions may stretch the design too wide, and low resolutions my make the content too narrow.
Pixel values are useful because they always remain a constant size regardless of resolution used. This is useful to help ensure your design is always going to be the same proportion regardless of your recipients screen resolution they have set up. Common resolutions for email newsletters are 600 or 800 pixels wide.