Unlike a book, a website contents never remain static.  It needs to be updated and kept freshed all the time.  Your site may require the following services from time to time and it is a good idea to hire a professional company for its maintenance to save time and money.  You site may need the following and more:

• Add or change products & services
• Updates to calendar or events
• Manage breaking news or upcoming events
• Manage photos, graphics, graphs and charts
• Text may be re-written and improvements made
• Site Management
• Repairing dead links
• Shopping cart product updates
• Update announcements, articles etc
• Creation of PDF or lies in other formats and uploading these.

Programming sites with databases require additional maintenance such as backup of all websites files, databases, fix server setting issues, etc that arise from time to time.