title: Error: $.jgrid. is not a function
body: <p>When I play my PHP/JS project in Firefox some errors happen and the grids often do not load.</p>
  
  <p>The errors – shown by Firebug – are each time different in number and type.</p>
  
  <p>For example…</p>
  
  <p>… on first start…</p>
  
  <pre><code>$.jgrid.extend is not a function
  restoreRow : function(rowid, afterrestorefunc) {
  </code></pre>
  
  <p>… after pressing F5…</p>
  
  <p>no error happens</p>
  
  <p>… after a further F5…</p>
  
  <pre><code>$.jgrid.extend is not a function
  getChangedCells : function (mthd) {
  grid.celledit.js (riga 448)
  $.jgrid.extend is not a function
  toggleSubGridRow : function(rowid) {
  grid.subgrid.js (riga 265)
  $.jgrid.extend is not a function
  addChildNode : function( nodeid, parentid, data ) {
  grid.treegrid.js (riga 545)
  $.jgrid.extend is not a function
  "avg" : function(v, field, rc) {
  grid.grouping.js (riga 286)
  $.jgrid.extend is not a function
  filterToolbar : function(p){
  grid.custom.js (riga 128)
  $.jgrid.extend is not a function
  excelExport : function(o) {
  grid.import.js (riga 179)
  $.jgrid.extend is not a function
  gridResize : function(opts) {
  grid.jqueryui.js (riga 471)
  b.jgrid.jqID is not a function
  n=0,p;for(p=0;p&lt;a.p.colModel.length;p+…a.p.id)+" tbody:first tr:first")[0];
  jquery….min.js (riga 54)
  b.jgrid.jqID is not a function
  M),I={};G=G.slice((N-1)*M,N*M);n=w=nul…load_"+b.jgrid.jqID(a.p.id)).hide();
  jquery….min.js (riga 75)
  b.jgrid.jqID is not a function
  M),I={};G=G.slice((N-1)*M,N*M);n=w=nul…load_"+b.jgrid.jqID(a.p.id)).hide();
  jquery….min.js (riga 75)
  b.jgrid.jqID is not a function
  M),I={};G=G.slice((N-1)*M,N*M);n=w=nul…load_"+b.jgrid.jqID(a.p.id)).hide();
  jquery….min.js (riga 75)
  b.jgrid.jqID is not a function
  n=0,p;for(p=0;p&lt;a.p.colModel.length;p+…a.p.id)+" tbody:first tr:first")[0];
  jquery….min.js (riga 54)
  b.jgrid.jqID is not a function
  n=0,p;for(p=0;p&lt;a.p.colModel.length;p+…a.p.id)+" tbody:first tr:first")[0];
  jquery….min.js (riga 54)
  b.jgrid.jqID is not a function
  n=0,p;for(p=0;p&lt;a.p.colModel.length;p+…a.p.id)+" tbody:first tr:first")[0];
  jquery….min.js (riga 54)
  b.jgrid.jqID is not a function
  M),I={};G=G.slice((N-1)*M,N*M);n=w=nul…load_"+b.jgrid.jqID(a.p.id)).hide();
  </code></pre>
  
  <p>… and after a further F5…</p>
  
  <p>other 15 similar errors happen.</p>
  
  <p>In the main page of the project I included the libraries as follows:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
     &lt;head&gt;      
        &lt;title&gt;&lt;/title&gt;        
        &lt;link type="text/css" href="js/jquery/css/cupertino/jquery-ui-1.8.13.custom.css" rel="stylesheet" /&gt;    
        &lt;script type="text/javascript" src="js/jquery/js/jquery-1.5.1.min.js"&gt;&lt;/script&gt;
        &lt;script type="text/javascript" src="js/jquery/js/jquery-ui-1.8.13.custom.min.js"&gt;&lt;/script&gt;
        &lt;link rel="stylesheet" type="text/css" media="screen" href="js/jqGrid/src/css/ui.jqgrid.css" /&gt;
        &lt;script src="js/jqGrid/js/i18n/grid.locale-it.js" type="text/javascript"&gt;&lt;/script&gt;
        &lt;script src="js/jqGrid/js/jquery.jqGrid.min.js" type="text/javascript"&gt;&lt;/script&gt;
        &lt;script src="js/jqGrid/src/grid.loader.js" type="text/javascript"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>I'd like to know what's wrong. Thanks,</p>