When I add <a href> to code blocks it breaks my homepage

Site URL: https://dragonfly-pentagon-ym6h.squarespace.com/

site password is 123

I used code blocks to create a mouse hover-over effect on the three top images on my homepage. When I add, let's say 

<a href="https://dragonfly-pentagon-ym6h.squarespace.com/directory"> (or any other link to any other of these images) so that when you click on the blue image, it goes to the directory page, the click area seems to expand to the section below so no matter where my mouse is, any click will act as if I've clicked that hyperlink. It also increases the size of the section below.

What gives?

Here's the code I used for each of these code blocks:

<a href="https://dragonfly-pentagon-ym6h.squarespace.com/directory">
<img src="https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625345f3de22634c0986fa0d/1649624563271/searchVectorPart1.png
" onmouseover="this.src='https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625344a058497c282010c687/1649624224879/searchVectorsecond.png'" onmouseout="this.src='https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625345f3de22634c0986fa0d/1649624563271/searchVectorPart1.png'">

Hi,

Your a tag missing closing tag

If you use <a> you need to add a closing </a>

<a href="https://dragonfly-pentagon-ym6h.squarespace.com/directory">
<img src="https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625345f3de22634c0986fa0d/1649624563271/searchVectorPart1.png" onmouseover="this.src='https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625344a058497c282010c687/1649624224879/searchVectorsecond.png'" onmouseout="this.src='https://static1.squarespace.com/static/6238af5e19bb205556416810/t/625345f3de22634c0986fa0d/1649624563271/searchVectorPart1.png'">
</a>

For those interested elements without closing tags are known as empty elements. As @tuanphan points out the a tag is not one of them. Not closing non-empty tags can produce very odd page renderings!

There is a list of allowed empty elements on MDN.

Thanks guys, that was it