Experience level = Beginner

One of the common reasons that a site fails to operate correctly is corrupt or missing files. There are many Joomla extensions that will update/replace the core files. But by uploading them manually you can verify that all the files have been replaced correctly. Using the Joomla full package to update is an alternative to using an update patch. Occasionally the wrong update patch is applied and, as a result, and important files fail to be updated.
The following link shows a tutorial video that demonstrates how easily and quickly it can be achieved.  It demonstrates the replacing of 1.5 but the same method can be used for any version of Joomla.  Just make sure that you use the latest update for the Joomla version that you are using.  The software used is Filezilla FTP client.  It is simple to setup and only requires ftp server, username & password to be entered. Once that is done you can connect your computer to the Server containing the files on your site. Navigating those is as easy as navigating the files on your PC.
If any of the files failed to transfer it is most likely caused by bad file permissions. Having identified the path and name of any file(s) that failed to transfer. You need to locate the recipient file on the Server and set it so it can be overwritten. The following link shows a tutorial on setting the correct permissions. Care must be taken to set the correct values. The process is simple enough and takes a matter of seconds rather than minutes or hours.  This is also the same method for updating and upgrading some versions of Joomla.





Additional information :


 This method is also used for updating Joomla 1.0.x and 1.5.x


When replacing image files it is often best to delete the files then refresh the Browser before uploading new ones.  This will clear the Browser cache of the old images.  This was used on a Graphic design site recently to enable viewing of the new images.  Also the image slider needed to have the cache cleared in order to display the new images.  The Graphic print on the page was automatically refreshed with each page visit.