Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day.
IIS is able to impersonate the IUSR_<computername> account because the user name and password for this account are known by IIS. Before returning a page to the client, IIS checks NTFS file and directory permissions to see if the IUSR_<computername> account is allowed access to the file.
I'm trying to get rid of a permission issue over UNC path where IIS can't read the web.config and tried to add IIS_IUSRS to the security tab of the web.config file but it has no idea what IIS_IUSRS is...when I try to search for users to add to the security list on that file in windows explorer in Win 7.