CDN Stands for Content Distribution Network or also called Content Delivery Network is a group of computers placed at various points connected with network containing copies of data files to maximize bandwidth in accessing the data. In CDN a client access a copy of data nearer to the client location rather than all clients accessing
from the one particular server. This helps to achieve better performance of data retrieval by client.
There are two leading CDNs available that hosts jQuery files.
Microsoft - To load jQuery from Microsoft AJAX CDN
jQuery file can be loaded from Microsoft AJAX CDN. For more details, go to http://www.asp.net/ajaxlibrary/cdn.ashx. You will need to keep following tags in your page.
Google - To load jQuery from Google Libraries API
jQuery file can be loaded from Google CDN for more details, go to http://code.google.com/apis/libraries/devguide.html. You will need to keep following tag in your page.