HTTP Error 503 : The Services is Unavailable In SharePoint 2010.

For following ERROR--
 when open site give error-----"HTTP Error 503 : The Services is Unavailable."
AND evenr viewer give Massega ----

 "The Execute method of job definition Microsoft.Office.Server.Search.Administration.IndexingScheduleJobDefinition (ID 4e7ccb2c-ed17-45fe-898a-14708df2bd6c) threw an exception. More information is included below."

 The password of the search service account has expired. To update the password visit the services on server page and update the password for the search service.

Then you need to reset Password by following way------------
(a) Reset password in AD

(b) Reset Password on STSADM
stsadm -o updatefarmcredentials -userlogin  DomainName\UserName  -password NewPassword -local
stsadm -o updateaccountpassword -userlogin DomainName\UserName  -password NewPassword -noadmin
stsadm.exe -o spsearch -farmserviceaccount DomainName\UserName  -farmservicepassword NewPassword
stsadm.exe -o spsearch -farmcontentaccessaccount DomainName\UserName -farmcontentaccesspassword NewPassword
stsadm.exe -o editssp -title SharedServicesProviderName  -ssplogin DomainName\UserName -ssppassword NewPassword
stsadm.exe -o osearch -farmserviceaccount DomainName\UserName  -farmservicepassword NewPassword


/////////////////////////OR  OR OR  OR OR  OR OR  OR /////////////////////////////////

1.    goto services.msc  and update password for Administrator account (Log on As) .
2.    goto application pool and update password for Administrator account (Identity) .
           for 2 right click on application pool(wher Identity is Administrator) 
                  Advance sitting -> click on Identity and set password