PO fields Order

Hi

I found a weird error today when i was creating PO.

The fields were not appearing in the correct sequence.

Normally in the item level, we have fields:-

Item     Acc. Asst     Item Cat.     Material     quantity     UoM     Delivery data             ........etc

But today the fields were appearing like:-

Item     material     quantity     Plant     Sloc     Returns Indicator     Acc.Asst         UoM     Item Cat,,,,,,,etc

Why this happened and how to correct this,

Regards

Amit