Hello,
Ellipses are suported only in certain browsers.
You can do this in css extending the cell content – something like
.ui-jqgrid tr.jqgrow td : { text-overflow:ellipsis;}
but this will work only in IE.
If you want to do this in other browsers, you maybe need to look here:
http://www.jide.fr/emulate-text-overflowellipsis-in-firefox-with-css
Regards
Tony