Can we detect whether JavaScript is enabled at the client from within JSP?

You can make use of the JavaBean called BrowserHawk4J from a company called Cyscape for this purpose. This bean allows you to detect a wide array of things at the client from the server-side, including the enablement of Javascipt to the presence of ActiveX controls for Flash, Quicktime, etc. See http://www.cyscape.com for details.