XHTML: The X stands for "Extensible", and this kind of HTML works hand in hand with XML (eXtensible Markup Language) to enable people to create more customized tags with specific behaviors attached to each one.
With the advent of dynamically generated sites, a great deal of HTML has been replaced by more suitable languages such as eXtensible Markup Language (XML) and Cascading Style Sheets (CSS).
At its core, RSS is written in Extensible Markup Language (XML) and the first element required in an RSS feed is the declaration: <?xml version="1.0"?>.
There is set up at once a certain hydrostatic pressure, due to the turgidity which ensues upon such absorption, and the extensible cell wall stretches, at first in all directions.
Pelecanus or Pelecanus), a large fish-eating water-fowl, remarkable for the enormous pouch formed by the extensible skin between the lower jaws of its long, and apparently formidable but in reality very weak, bill.