ALIGN sets the horizontal alignment of the cells in the row. One of the most common situations where ALIGN is useful is when you have a row of table headers that you want to align left with the text instead of being centered. So, for example, this code sets the first row of cells to align left:
HTML 4.0 says that HALIGN sets the horizontal alignment of the cells, but HALIGN is currently poorly supported by the browsers while ALIGN is well supported. Stick to ALIGN for now.