There is much spelling and grammar complexity in the Russian language. Fortunately, there are official rules which help you write correctly without consulting a dictionary every time. This is a web version of the Russian language rules:
The relevant rules are found as you type the letters you are unsure about:
The website automatically adapts to mobile phones:
To instantly find and read the rules offline, install the iPhone app.
Art director and developer
See also the 2010 version.