Project: selector
Task (challenging): modify css for elements in `#table`:
- append in cell(1,4) with: 
  `<a href="#table">table</a>
    <a href="#form">form</a>
    <a href="index.html">test</a>` 
  - set default links `text-decoration` to `underline`
  - set visited links `text-decoration` to `none`
  - set active links `outline` to `1px solid blue`
- set page's targeted element `background-color` to `lightgreen`
- do not use `!important` anytime