Click on "Tax Information & Services"
Under "TAX SERVICES" head click on "TAX PAYMENT"
Then Click on "PAY TAX ONLINE" ( A New window will Pop up where you have to click "YES"
Under NON-TDS/TCS CLICK ON CHALLAN ITNS 280
Remember that before filling up details, you click on radio button "INCOME TAX OTHER THAN CO."
You can see procedure for filing online service tax here.