Hi Durga;
Are you using the demo cloud edition. There was some known error as mentioned in the below thread. It should be working fine now.Just clear all the browser cache and cookies and try again.
Sap Fiori Demo Apps page error | SCN
Also, If still you getting the error, try below
Open Web IDE portal in a private/incognito window by adding '?settings=ignore' to the end of the url
e.g. https://webide-pxxxtrial.dispatcher.hanatrial.ondemand.com?settings=ignore
Regards,
Sarbjeet Singh