I'd like to write a bookmarklet for Chrome. Something like this.

<a href="javascript:void%20function(){var%20a=prompt(%22What%20is%20your%20name%3F%22,%22Your%20Name%22);null!=a%26%26alert(%22Hello%20%22+a)}();">
Oxford Extra
</a>

It works. On a real page one can drag this link to the bookmark panel and drop there.

The problem is that there is no icon.

If it were an ordinary link, the favicon of a site would appear. But in case of this bookmarklet, the Chrome's default icon is selected, which is not good.

How can I give the bookmarklet an icon?