Change Asp.net Ajax tab page header from javascipt

This is not as straightforward as you might have thought. To access the tab pages use get_tabs()[indexOfTab] as shown below.

$find('ctl00_cphMainContent_tc1').get_tabs()[0]) ; // tab 0
$find('ctl00_cphMainContent_tc1').get_tabs()[1]) ; // tab 1

To set the tab header use the _header of the tab
 $find('ctl00_cphMainContent_tc1').get_tabs()[0]._header.innerHTML='Tab 0';
 $find('ctl00_cphMainContent_tc1').get_tabs()[1]._header.innerHTML='Tab 1';

Cheers
Samitha