What is it that you want to do if there a rows that have changed between Inserted and Deleted? Perhaps insert into an audit log?
Then, ya gotta think in sets instead of IF's...
INSERT INTO AuditLog
(PK,OldValue,NewValue,ColumnName)
SELECT PK_Col AS PK,
d.df_SiteName AS OldValue,
i.df_SiteName AS NewValue,
'df_SiteName' AS ColumnName
FROM Inserted i
INNER JOIN Deleted d
ON i.PK_Col = d.PK_Col
AND ISNULL(i.df_SiteName,'') <> ISNULL(d.df_SiteName,'')