Build a webservice website for educational purposes

I need a simple solution with a simple design to teach visitors to a proper usage of language articles 'a','an', and 'the'. Webservice would accept text, or a link to a source article as an input, and processes the output in a way that all articles will be extracted from the output with a set of simple logic rules. The output will be displayed on the page with all the articles removed, however, the page should keep track of articles that were removed, so that the reader can read the text, and play the exercise of clicking on the empty space before the nouns, and if the article was removed from the space, it would be inserted in place, and if not, the area under the cursor would be highlighted in some pale-red color signifying that article would not need to be inserted there. Once reader finishes reading the text, they can check themselves one more time by clicking on Submit button, and all the areas that were not checked/clicked before, would show up, highlighted by some other distinct color. The application should accept Input as a plain text field, or a URL. If a URL is entered, the article should be extracted from the page and processed completely, removing all the ads and other metadata, leaving just to text to be practiced on.