I use JS here and there mainly for slideshows, form validation, drop down sitenav (next step) but I have a few noobie questions if some one has the time...

I have been able so far just to use a jquery library on my server but recently start using a calendar for clients to select a date of birth. The calendar required these sources.

```
<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
  <script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>

```

My instinct tells me I should have these .js and .css files on my server, is it bad practice to use http sources? I'm currently keeping the links because I need to reference these libraries from different directories of my site.

Are these jquery plugins or is it Ajax? as they're not in the main jquery library. I thought Ajax was an MS alternative to JQuery but now I'm confused... Is there a common large library people like to use or is it common to just add smaller ones here and there?

Any help much appreciated.