Leo

Leo (♌) is the 5th astrological sign of the Zodiac, originating from the constellation of Leo. In astrology, Leo is considered to be a "masculine", positive (extrovert) sign. It is also considered a fire sign and is one of four fixed signs. Leo is ruled by the Sun. Being the fifth sign of the zodiac, Leo has been associated with the astrological fifth house.

Individuals born when the Sun was in this sign are considered Leo individuals. The Sun is in Leo roughly from July 23 to August 22. Under the sidereal zodiac, it is currently there roughly from August 10 to September 15. The Sanskrit name of Leo in Hindu astrology is Siṃha.

Compatibilities
Based on Elements within the Zodiac, Leo is considered compatible with Aries, Sagittarius and Leo itself.
There are many variables that determine compatibility in astrology, such as birth dates, birth months, birth years, position of a sign within the Sun, the Moon, Stars. The signs listed as compatible with Leo do not reflect an individual profile or individual reading as interpreted within astrology, but rather reflect a general guideline and reference to compatibility as dictated by variables such as Qualities and Elements within the Zodiac. The branch of astrology dealing with interpersonal compatibilities is called Synastry.
Source : http://en.wikipedia.org/wiki/Leo

Cancer

Cancer (♋) is the fourth astrological sign in the Zodiac, originating
from the constellation of Cancer. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Cancer is considered a "feminine", negative (introvert) sign. It is also considered a water sign and is one of four cardinal signs. Cancer is ruled by the Moon. Being the fourth sign in the zodiac, Cancer has been associated with the astrological fourth house.

Individuals born when the Sun was in this sign are considered Cancer individuals. Under the tropical zodiac, the Sun enters Cancer on the moment of summer solstice by definition, or roughly on June 22, leaving it around July 23. Under the sidereal zodiac, it is currently roughly from July 16 to August 15. The Sanskrit name of Cancer in Hindu astrology is Karka.

Compatibilities
Based on Elements within the Zodiac, Cancer is considered compatible with Scorpio, Pisces and Cancer itself.
There are many variables that determine compatibility in astrology, such as birth dates, birth months, personalities, birth years, position of a sign within the Sun, the Moon, Stars, etc. The signs listed as compatible with Cancer do not reflect an individual profile or individual reading as interpreted within astrology, but rather reflect a general guideline and reference to compatibility as dictated by variables such as Qualities and Elements within the Zodiac. The branch in astrology dealing with interpersonal compatibilities is called Synastry.
Source : http://en.wikipedia.org/wiki/Cancer