Explanation:

 A planet's axial tilt is a measure of whether the planet is in prograde (the natural direction of rotation of most bodies in our solar system) or retrograde (the opposite, ie, from East to West) rotation. Tilt angle is measured relative to the orbital plane of a planet. A tilt between 1 to 90 degrees is considered prograde rotation (Earth's tilt is 23 degrees, in prograde rotation), a tilt of 90 degrees is considered perpendicular, and neither prograde or retrograde. However, a tilt of anything greater than 90 degrees is considered retrograde rotation. Uranus's axial tilt is almost 98 degrees, and Venus's tilt is 177 degrees. So they're both considered to have retrograde rotation

Venus
Currently, the most popular theory states that Venus did indeed rotate in the same direction as the rest of the planets. But at some point of time, something caused the planet to flip 180 degrees around its axis. This could have been a collision of a large body at an angle that got absorbed into Venus, or due to some unknown cause. So it continued spinning in the same direction, but flipped itself over. So the rotation looks reversed to us.

Venus is also in a spin-orbit resonance with the Earth and this has been thought to have influenced Venus's rotation. Spinning bodies create certain ratios of gravitational forces that act on each other, and create specific ratios of resonances. In our Solar System, the 3:2 resonance seems to be quite common. The Sun and Mercury are in a 3:2 lock (a day on Mercury is 58.646 days and a year is 87.969 days), as are Neptune and Pluto, and Jupiter with 3:2 orbital resonance with the Hilda asteroids. Venus completes three Venusian days for every two revolutions Earth makes around the Sun.

Some people also believe that there could also have been major storms on one side of the surface of Venus that could have altered the direction of rotation.

The newest theory that French astronomers have proposed is that Venus's rotation kept slowing down and finally hit a stop, and then the planet started spinning in the opposite direction (called a retrograde rotation). The sun's gravitational pull is very strong on Venus and Mercury, making their rotations very slow and their days longer than their years. Venus's period of rotation is 254 days, while a Venusian year is only 224 days. This is because of very slow rotation influenced by the extremely strong gravitational force exerted by the Sun. In fact, there is evidence to suggest that Venus's speed of rotation is currently slowing down.

Uranus
Scientists earlier believed that an object the size of two Earths hit the surface, causing the plant to tilt. However, this doesn't explain why Uranus's moons have the same tilt. So the theory that is accepted currently is that Uranus was pummeled by multiple bodies the size of Earth or two Earths and tilted on its axis much before its moons were formed.

In the Solar System, all of the planets and most of the other objects that orbit the Sun, with the exception of many comets, do so in the "prograde" direction, i.e. the same sense as the rotation of the Sun. Also the rotations of most planets are prograde, with the exceptions of Venus and Uranus, which have retrograde rotations. Most satellites of planets revolve around their planets in the prograde sense. (In the case of the satellites of Uranus, this means they revolve in the same sense as Uranus's rotation, which is retrograde relative to the Sun.) There are some satellites which orbit in the retrograde sense, but these are generally small and distant from their planets, except for Neptune's satellite Triton, which is large and close. It is thought that these retrograde satellites, including Triton, are bodies which have been captured into orbit around their planets, having been formed elsewhere.