Working with White Lists 
Authorized severs and folders that are needed for HTTP-based communication of Web Dynpro UI elements are listed in a white list. A certificate is stored by the administrator on every application server to validate white lists.
File upload, file download, and the execution of programs will not work correctly without a white list.
To be able to work with a white list, you first need a certificate for the affected SAP system. This certificate is stored in table WDR_ACF_WL_CERT.
You therefore must have created a certificate using transaction WDR_ACF_GEN_CERT (see Creating Certificates).
Library SAPCRYPTOLIB must also be installed. For more information, see SAP Note 455033—SAPCRYPTOLIB. Use transaction STRUST to check the installation of SAPCRYPTOLIB and to determine if entry SAPCRYPTOLIB exists.
Continue with Creating Certificates.