Strange behavior A HREF code

Hi,

I use the following code to display a row of icons with a link:
<a href="https://thekey.nl/who"><img src="https://thekey.nl/wp-content/uploads/2018/07/kennismaking.png" alt="The Key WHO" border="0" /></a>  <a href="https://thekey.nl/bedrijfsaanbod"><img src="https://thekey.nl/wp-content/uploads/2018/07/presentatie.png" alt="The Key WHO" border="0" /></a>  <a href="https://thekey.nl/bedrijfsaanbod"><img src="https://thekey.nl/wp-content/uploads/2018/07/BEZICHTIGING.png" alt="The Key WHO" border="0" /></a>  <a href="https://thekey.nl/contact"><img src="https://thekey.nl/wp-content/uploads/2018/07/tekenen.png" alt="The Key WHO" border="0" /></a>  <a href="https://thekey.nl/contact"><img src="https://thekey.nl/wp-content/uploads/2018/07/ontvang-sleutel.png" alt="The Key WHO" border="0" /></a>

It displays well, but when I hover over the icons the layout is messed up pretty bad. Any idea what is going on?
See this page (https://thekey.nl/test/) for this problem.
THX Freek