Hello Alpesh,
Unfortunately, the emptyDataString message does not support HTML content, only plain text. As a workaround, you can make a jQuery selection of the label and set your content as follows:
$(".jqx-grid-empty-cell span").html("<em>Custom no data to display message.</em>");
Note, however, that this will work only until you scroll/edit/refresh the grid and after that you will have to call the same code again to maintain the customized appearance of the label.
Best Regards,
Dimitar
jQWidgets team
http://www.jqwidgets.com/