HTML-encoding values can help prevent cross-site scripting attacks and malicious content from being displayed. HTML encoding is also useful when you want to display HTML code in the browser, such as displaying the string "<br/>" instead of inserting a line break (<br/> element) in the page.
This property is new in ASP.NET 3.5. Setting this property to false restores the default behavior of the DataFormatString property in versions of ASP.NET earlier than 3.5. For more information, see the DataFormatString property.