Cómo mostrar la hora digital en HTML

 < 
 html 
 > 
 < 
 head 
 > 
 < 
 script 
 type 
 = 
 "text/javascript" 
 > 
 function 
 startTime 
 () 
 { 
 var 
 today 
 = 
 new 
 Date 
 (); 
 var 
 h 
 = 
 today 
 . 
 getHours 
 (); 
 var 
 m 
 = 
 today 
 . 
 getMinutes 
 (); 
 var 
 s 
 = 
 today 
 . 
 getSeconds 
 (); 
 // add a zero in front of numbers<10 
 m 
 = 
 checkTime 
 ( 
 m 
 ); 
 s 
 = 
 checkTime 
 ( 
 s 
 ); 
 document 
 . 
 getElementById 
 ( 
 'txt' 
 ). 
 innerHTML 
 = 
 h 
 + 
 ":" 
 + 
 m 
 + 
 ":" 
 + 
 s 
 ; 
 t 
 = 
 setTimeout 
 ( 
 'startTime()' 
 , 
 500 
 ); 
 } 
 function 
 checkTime 
 ( 
 i 
 ) 
 { 
 if 
 ( 
 i 
 < 
 10 
 ) 
 { 
 i 
 = 
 "0" 
 + 
 i 
 ; 
 } 
 return 
 i 
 ; 
 } 
 </ 
 script 
 > 
 </ 
 head 
 > 
 < 
 body 
 onload 
 = 
 "startTime()" 
 > 
 < 
 div 
 id 
 = 
 "txt" 
 ></ 
 div 
 > 
 </ 
 body 
 > 
 </ 
 html 
 >