I try to load this mapserver raster into QGIS, using ArcGIS REST API Connector plugin:
but i get an error- how can i do it?
You are using the wrong panel and the wrong URL.
Go into Layer->Add Layer->Add ArcGIS MapServer Layer Create a new server connection and use this URL: http://www.sol-israel.co.il/arcgis/rest/services/ORTHO_LACHISH_Mapi/MapServer
You can now load the layer 0 you were interested in.