Hello I want to use a xbee connect to my webserver for send inforamtion to a xbee connect to arduino UNO.
Is your webserver YOUR computer? If not, how do you propose to connect the XBee to the web server?
What is the best language to use webpage to make somr button like on / off or slide button to fade the led connected to arduino.
At the core, web browsers know how to request data from web servers. Typically, the web server responds with html that the browser parses and renders.
The data stream returned by the web server can include tags that the browser recognizes as triggers for external parsers (like PHP) that parse some of the data stream, and substitute other data in it's place (typically more html).
So, the "best language" is html.
Of course, there are other languages that make generating the html easier, but what you want to do can be done entirely in a form on a web browser using nothing but html.