left join , Unknown column 't1.itemid' in 'on clause'

[wang shuming]

Hi,
  select * from t1,t2
  left join t3 on t3.itemid=t1.itemid

  mysql4.1 works, but mysql5.0 shows  Unknown column 't1.itemid' in 'on clause'

 If change into
  select * from t2,t1
  left join t3 on t3.itemid=t1.itemid

  mysql5.0 works

Shuming　Wang