help for add extra col with tag html by sAjaxSource

mcpalls

hello boys, i have a problem for add extra col, i have tried a lot of examples:
http://www.datatables.net/blog/Drill-down_rows
http://www.datatables.net/release-datatables/examples/api/row_details.html
...
but it don't work
the error is:
DataTables warning (table id = 'datatable'): Requested unknown parameter 'browser' from the data source for row 0

my code is:
[code]
"bProcessing": true,
"bServerSide": true,
"sAjaxSource": "server_processing.php",
"aoColumns" : [ {
"mData" : "browser",
"bSearchable" : false,
"bVisible" : false
}, {
"mData" : "platform",
"bSearchable" : false,
"bVisible" : false
}, {
"mData" : "version"
}, {
"mData" : "grade",
"bSearchable" : false,
"bVisible" : false

}, {
"mData" : null,
"bSearchable" : false,
"bSortable" : false,
"fnRender" : function(oObj) {
return '';
}
}]
[/code]

html code:
[code]


Browser
Platform(s)
version
grade





Loading data from server


[/code]
php array for query:
[code]aColumns = array( 'browser', 'platform', 'version', 'grade');[/code]

at the end my debug:
http://debug.datatables.net/ibenuk

i spent more than 4 hours to fix it but nada, am i an idiot ? :)
and for now goodnight...
tnk for all.

mcpalls

ohh yeaahh i solved
[code]
"aoColumns" :
[ null, null, null, null,
{
"mData" : null,
"bSearchable" : false,
"bSortable" : false,
"fnRender": function ( data, type, full ) {
return 'delete';
}
}


]
[/code]

but why with null,null,null,null, it's ok?