Why I can't change font size for label?

Question

I have little problem and don't know why it doesn't work. I tried to change font size for label tag, but I can't set less than 10px. Why?

.group {
  margin-bottom: 20px;
}
.group label {
  font-size: 10px;
}
.group2 label {
  font-size: 8px;
}

<div class="group">
  <label for="input1">First label</label>
  <input type="text" name="input1">
</div>
<div class="group group2">
  <label for="input2">Second label</label>
  <input type="text" name="input2">
</div>

Answer 1

I have tested this one on my side and it works as intended.

If you are loading the styles via a stylesheet it is possible that your browser has cached this, and you may need to clear browser caches.

Some browsers do also supply default values for most HTML elements. (Something to consider)

Answer 2

EDIT: It turned out that cached CSS in Opera was responsible non-updating styling.

Working as required. Remember to re-run your code snippet after making changes.

.group {
  margin-bottom: 20px;
}
.group label {
  font-size: 10px;
}
.group2 label {
  font-size: 4px;
}

<div class="group">
  <label for="input1">First label</label>
  <input type="text" name="input1">
</div>
<div class="group group2">
  <label for="input2">Second label</label>
  <input type="text" name="input2">
</div>