How to write CSS code for different window widths

Writing CSS code to get different windows width will require you to make use of display:none which applies to all width less than 700px to achieve the result you want use the procedure below:

Since

 #right { display:none}

applies for all widths less than 700, you can add it in

@media (max-width:700px).

Use max-width media queries in descending order and keep changing the styles for the lower width screens.