To require a column to be a certain minimum width, you can insert a spacer image into that column. For more information, see Spacer images. You can remove spacer images from a single column or from the entire table.
The first time you insert a spacer image, you set up a spacer image for the site. You can set preferences for spacer images (see Setting preferences for Layout mode).
If you have not set a spacer image for this site, the Choose Spacer Image dialog box appears.
For more information, see Setting the Choose Spacer Image dialog box options.
Dreamweaver inserts the spacer image into the column. The image is not visible, but the column might shift slightly and a double bar appears at the top or bottom of the column to indicate that it contains a spacer image.
Dreamweaver removes the spacer image. The column might shift.
The layout of your whole table might shift. If there is no content in some columns, the columns might disappear completely from the Design view.