The purpose of this dialog box is to convert layers to tables for better compatibility with older browsers.
Most Accurate creates a cell for every layer, plus any additional cells that are necessary to preserve the space between layers.
Smallest: Collapse Empty Cells specifies that the layers edges should be aligned if they are positioned within the specified number of pixels.
If you select this option, the resulting table will have fewer empty rows and columns, but may not match your layout precisely.
Use Transparent GIFs fills the tables last row with transparent GIFs. This ensures that the table is displayed with the same column widths in all browsers.
When this option is enabled, you cannot edit the resulting table by dragging its columns. When this option is disabled, the resulting table will not contain transparent GIFs, but the widths of the columns may vary from browser to browser.
Center on Page centers the resulting table on the page.
If this option is disabled, the table starts at the left edge of the page.