Hi Raju,
Masthead customization and configuration are available in this liks
Masthead Customization in NW 7.31
How to download and change AFP Masthead on SAP Portal 7.3
In Masthead HeaderiView.jsp is available,In that you need to try this below code for clock.
<TABLE >
<TR><TD>
<FORM NAME="clock_form">
<INPUT align="right" TYPE=TEXT NAME="clock" SIZE=35>
</FORM>
<SCRIPT LANGUAGE="JavaScript">
<!-- Hide from non JavaScript browsers
function clockTick()
{
currentTime = new Date();
document.clock_form.clock.value = " "+currentTime;
document.clock_form.clock.blur();
setTimeout("clockTick()", 1000);
}
clockTick();
// End of clock -->
</SCRIPT>
</TD></TR>
</TABLE>
i hope it helps.
Best Regards
Durga.