to the Right buttons to create new columns in your layout table.   Working with Autostretch Tables As I mentioned earlier, Dreamweaver refers to tables and cells that span a width of 100% as Autostretch tables in Layout mode. Although tables and cells are assigned fixed widths when they're drawn on the page, you can always convert a fixed-width table or cell to an Autostretch table or cell by selecting the Autostretch radio button in the Properties Inspector when either the layout table or layout cell is selected. A second option is to choose the Make Column Autostretch option from the Column Widths Visual Aid's menu. To demonstrate the use of the Autostretch option, select the Header layout table. Next, click the Autostretch radio button in the Properties Inspector. The Choose Spacer Image dialog appears, similar to Figure 6.47. Figure 6.47. Selecting the Autostretch radio button in the Property Inspector opens the Create Spacer Image dialog.   Spacer images are generally 1-pixel by 1-pixel transparent GIF images and can be inserted into a table cell and given a fixed width attribute in pixels. The spacer image stabilizes the column containing that cell, preventing it from shrinking any smaller than the dimensions of the spacer. If you define a column as Autostretch, and other columns in the table don't have some sort of content in them propping them open, the stretching column shrinks the other columns down to nothing, regardless of what their fixed-pixel widths are. If your table's fixed columns contain content such as images, the images will keep the columns from shrinking. But in case they don't, this is the time to use a spacer image. As you can see from Figure 6.47, the Choose Spacer Image dialog contains the following options: Create a spacer image file: Choose this option to have Dreamweaver automatically create the 1-pixel by 1-pixel transparent GIF image for you. Dreamweaver places this image in the Default Images folder or, if this folder is not defined, in the root of your project. Use an existing spacer image file: Choose this option if you've created a spacer image already and would prefer to use it. Don't use spacer images for autostretch tables: Choose this option when you'd prefer not to use spacer images. This option is handy when you already have an image in a table or cell that is marked as Autostretch. You can also add a spacer image by selecting the Add Spacer Image option from the Column Widths Visual Aid menu. If you'd prefer to remove existing spacer images from all columns in a table, you can select the Remove All Spacer Images option from the Table Widths Visual Aid menu or select the Remove All Spacer Images icon from the Property Inspector. You can set Dreamweaver to automatically add spacer images when working with Autostretch tables by opening the Layout Mode category in the Preferences window. In Chapter 5, "Defining Preferences," we learned that the Layout Mode category contains options for setting color preferences in Layout mode as well as various spacer image preferences including a radio button that allows you to tell Dreamweaver to always use a spacer image when working with Autostretch tables. Refer to the previous chapter for more information. To round out our design, choose the Don't Use Spacer Images for Autostretch Tables option and click OK. Notice that the Header layout table now stretches to consume 100% of the Document window. To add the background image to the table, simply switch to Standard mode, select the table, and use the point-to-file icon in the Bg Image text box of the Property Inspector to point to the header_bg.gif image file in the Files panel. The result resembles Figure 6.48. Figure 6.48. Add the header_bg.gif image as a background to the Header table of our design.