An encoded string.
If characters such as blanks and punctuation are passed in an HTTP stream, they might be misinterpreted at the receiving end. HTML encoding converts characters that are not allowed in HTML into character-entity equivalents; HTML decoding reverses the encoding. For example, when embedded in a block of text, the characters < and > are encoded as < and > for HTTP transmission.
If the value parameter is null, then the returned encoded string is null. If the value parameter is an empty string, then the returned encoded string is an empty string.