Hi Dilip,
don't worry. Suppose if you have 4 columns col1, col2, col3 & cols & you use:
order by col1, col2, col3, col4
then sql server first orders by col1,
then col2
then col3
then col4
means if col1 has some rows which have same value, the sql server arrange the results by col2.
means precedence left to right.