I started learning Chrome Extensions last week and haven't stopped since! And here is my first Chrome extension:
https://chrome.google.com/extensions/detail/jljcgbhckfkcjngjdmadimlkfjgoacal?hl=en-gb
It's called Miniclip Improved. It fixes all the adds (removing their 'stains') on miniclip.com.
Please Try it out!