is it true that the sun never set in 1st day of summer and never set in 1st day of winter(sep)?

If you live in the arctic the sun rises in spring and sets in autumn and is up all the time in summer.

If you live in the antarctic the sun rises in autumn and sets in spring and is up all winter.

Hope this helps.

BTW if you lived at the North pole sunrise will be 20:52 universal time 18th March 2011 and will set 25th September 2011 12:32 UT.

If you lived at the South pole, sunset will be 02:08 UT 23rd March 2011 and sunrise will be 05:46 UT 21st September 2011.

That's correct. If you are within about 23.5 degrees latitude of either pole, then you will experience at least one day of complete (24-hour) sunlight (around the beginning of summer), and at least one day of complete darkness (around the beginning of winter).

The closer you get to the pole, the more such days you experience. The exact number of days, and the dates on which they occur, depend on exactly what latitude you're at. For example, if you live at 80° North latitude, your year goes like this:

Jan 1 to Feb 21: Sun never rises (24 hours darkness)
Feb. 22 to April 15 : Sunrise/Sunset every day; days gradually get longer
April 16 to August 28 : Sun never sets (24 hours sunlight)
August 29 to Oct. 18: Sunrise/Sunset every day; days gradually get shorter
Oct. 19 to Dec. 31: Sun never rises (24 hours darkness)

The exact days are different for different latitudes. If you are right at the pole (±90°), the sun will stay up for 6 months, never setting; and then it will stay down for 6 months, never rising.

at both poles the sun doesn't set on midsummer's day

You need be be very close to the arctic circle, or inside it (that is, further north). Right on the arctic circle, the sun rises on June 6, and does not set until July 7th. About 92 km south of that, it rises on June 19 and sets on June 21, so it is up all day on June 20.

For the antarctic circle, the dates are December 22 and 23.