Just see what wrong with your link
<a href=" " />
This is self-closing anchor tag here the href takes the link or path inside double inverted comma i.e ” “
Now in your link
<link rel="stylesheet" href="{% static "css/style.css" %}">
Here compiler takes href as
href="{% static "
which is inside double inverted comma and as soon as it discovers / (forward-slash) it thinks this / as the closing of link and expects for >.This is the reason its throwing error and giving unclosed tag error.
What the compiler is expecting
<link rel="stylesheet" href="{% static "css/>
This is the solution :
<link rel="stylesheet" href="{% static 'css/style.css' %}">
make sure you css/style.css is inside single inverted comma ‘ ‘