This is basically a repost of a forum post from the sencha site that can be found here. However, after spending a few hours looking for the solution to the dreaded question, ‘Why can’t I just copy the grid cells and paste them like I used to when the page was a HTML table?”. I thought that I would post the answer I found here so it could reach more people.

First, you will need to add the following CSS in your main stylesheet.

.x-grid-row ,.x-grid-cell, .x-unselectable, .x-unselectable * {
 -webkit-user-select: text !important;
 -o-user-select: text !important;
 -khtml-user-select: all !important;
 -ms-user-select: text !important;
 user-select: text !important;
 -moz-user-select: text !important;
} 

Next, just place the following code somewhere in the top of your application javascript file.

if(typeof Ext != 'undefined'){
  Ext.core.Element.prototype.unselectable = function(){return this;};
  Ext.view.TableChunker.metaRowTpl = [
   '<tr class="' + Ext.baseCSSPrefix + 'grid-row {addlSelector} {[this.embedRowCls()]}" {[this.embedRowAttr()]}>',
    '<tpl for="columns">',
     '<td class="{cls} ' + Ext.baseCSSPrefix + 'grid-cell ' + Ext.baseCSSPrefix + 'grid-cell-{columnId} {{id}-modified} {{id}-tdCls} {[this.firstOrLastCls(xindex, xcount)]}" {{id}-tdAttr}><div class="' + Ext.baseCSSPrefix + 'grid-cell-inner ' + Ext.baseCSSPrefix + 'unselectable" style="{{id}-style}; text-align: {align};">{{id}}</div></td>',
    '</tpl>',
   '</tr>'
  ];
 }