Complex sentence: Many people consider this kind of modification to be "gaming the system", and it is known that Google regards some kinds of search engine optimization tactics to be illegitimate, and penalizes pages and websites that use these techniques.
Split into simpler sentences: Many people consider this kind of modification to be "gaming the system". It is known that Google regards some kinds of search engine optimization tactics to be illegitimate, and penalizes pages and websites that use these techniques.