There is one error in the following code:
Code:
<p align="center"><input type="button" value="Delete Cookie" onclick="delete_cookie(keyword)"></p>
If you look at the delete_cookie function call, you are supposed to pass a string which is the cookie name you wish to remove in your case "keyword". In JS you need to enclose your string either in single or double quotes.
Try to use the following line instead of your above mentioned line
Code:
<p align="center"><input type="button" value="Delete Cookie" onclick="delete_cookie('keyword')"></p>
A good tutorial on cookies in JavaScript can be found here. You can use the code mentioned in it as it seems to be very simple code to do the cookie based operations.
Bookmarks