This is a cursor value that Mozilla used before CSS 3
cursor: cell was implemented. Since Gecko 1.8a6 (December 2004), CSS 3 cursor cell is supported and rendered properly, so there's no need to use
cursor: -moz-cell in newer stylesheets.
The -moz-cell cursor value is used to indicate a cell or set of cells which may be selected. The -moz-cell cursor (just like the cell cursor) is rendered as a thick plus-sign.
On the Windows platform, the -moz-cell cursor looks like this:
Related bugzilla item: Bug 163174: Support CSS3 cursors