title: JQuery and Scripts within the head of a document
body: <p>I have the following scripts listed in my header from various widgets within my website:</p>
  
  <pre><code>&lt;script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="//code.jquery.com/jquery-1.9.1.js"&gt;&lt;/script&gt;
  &lt;script src="//code.jquery.com/ui/1.10.4/jquery-ui.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Jquery and using library scripts is new to me (using my own js files are not) the first two lines of the scripts above are similar.  Can someone please explain if I need 1.4.1 as I have 1.9.0 - looking at it I would assume it is a later version of 1.4.1.  </p>
  
  <p>However removing it; my website does not work correctly so are these a plugin's or widget identification for individual items and the jquery.min.js is a common filename?</p>
  
  <p>My second part of the question, I see Goggle API's, AJAX and code.jquery; are these large library's I should use to find plugin's?  Should I rely on those websites or should I download these scripts and place on my server (could that possibly be breaching their usage?).  Or do web developers just rely on the above?</p>
  
  <p>Thank you</p>