Javascript is evolving. With newer version, more commands, new functionalities gets added. To get to know the version of javascript your browser supports, just save the following code as html and load it in your browser:
<script type=”text/javascript”>var jsver = 1.0;</script><script language=”Javascript1.1″>jsver = 1.1;</script><script language=”Javascript1.2″>jsver = 1.2;</script><script language=”Javascript1.3″>jsver = 1.3;</script><script language=”Javascript1.4″>jsver = 1.4;</script><script language=”Javascript1.5″>jsver = 1.5;</script><script language=”Javascript1.6″>jsver = 1.6;</script><script type=”text/javascript”>document.write(‘<p><b>Javascript version ‘ + jsver+ ‘ supported<\/b><\/p>’);</script>
Most of the times, you can expect the following results:
Javascript version 1.6 supported
Browser and javascript version supported are as below:
Firefox, Netscape 7/8, Mozilla, and Opera 7+ all support version 1.6
Netscape 6 supports version 1.5
Opera 6 supports version 1.4
Netscape 4.5, Opera 5, and Internet Explorer 6 support version 1.3
Netscape 4 supports version 1.2
The Relentless FrontEnd - Aackose Lal's Blog 
So I just started with this and the cooslne app works like a charm.. however when I try to write in my App I don’t receive any errors, but it never writes!SPDiagnosticsCategory spdiagcat = new SPDiagnosticsCategory(“Hello ULS”, TraceSeverity.Verbose, EventSeverity.Verbose); SPDiagnosticsService diagSvc = SPDiagnosticsService.Local; diagSvc.WriteTrace(100, spdiagcat, TraceSeverity.Monitorable, “Writing to the ULS log is not happening “, null);
Imsipserve brain power at work! Great answer!