For your own piece of mind it is best to backup your own sites. All too often it happens that backups aren’t correct because the time and date stamp for the files uploaded remains the same due to the incorrect method used to upload files. If you’re synchronising files sometimes the time and date stamp used can be that of the file which already resides within your space and therefore when it comes to backing up that file to an automated system it seems backed up and passes over the file leaving you with a backup of the outdated version. Your best approach when it comes to a backup is to keep all original image files (like PSD) as well as the compressed versions of the files you use on your site (GIF, JPG, PNG etc) and all HTML, PHP, CSS Files. This way if disaster ever occurs you have a backup that’s exactly how it should be and works how it should. These files can be easily kept, with todays various methods of backup to compact media such as CD-R DVD-R or even RW based media, there are very few sites that would be over the size of a 4.7Gb DVD so it’s not difficult to free up space on your computer if this is of concern. For your own piece of mind keep all the files pertaining to your site ….. backup is not a dirty word and performed regularly takes no time at all.