Drop Down Information

We have a website built from CSS/HTML
the site is up and running.
We would like to add the following feature
On a particular page on the site, we would like to enable a number of services/links. When you click on a link, it expands and displays more information relevant to that link. We want the user to click on the link, the information is expanded but we want the user to stay on the same page, the expanded information pushes everything on the page down. if the user clicks on the same link again, the expanded information minimises and the page is back to normal.
the formatting of the expanded information needs to fit within the formatting of the rest of the website.