Hi Maria,
Both uses SAP ABAP Webdynpro architecture in backend. More information is here on these links -
ESS 1.4
https://help.sap.com/erp2005_ehp_06/helpdata/en/f6/263359f8c14ef98384ae7a2becd156/frameset.htm
ESS 1.50
http://help.sap.com/erp2005_ehp_05/helpdata/en/25/340b0507434193adbfe3f8fc8896c7/content.htm
Hope this helps,
Regards,
Ashutosh Shukla