I have a problem with a code to build a grid

when i finish the grid model and the data

in all examples apear
var grid = new Ext.grid.Grid('grid-example', {
ds: ds,
cm: colModel <<<----- Here is the problem.
});

The Mozilla browser show me that the problem is in this line
and if i change the lines

var grid = new Ext.grid.Grid('grid-example', {
cm: colModel,
ds: ds <<<----- Here is the problem.
});


If any can help me that i don't know ?



PD: Sorry for my inglish because I'm Argentinian