HTML output conflict with jupyter styling

**Bug Description**
When outputting HTML using IPython library, the css affects the styling of Jupyter Notebook IDE itself.

**Code to Reproduce**
```
from IPython.core.display import display, HTML
testHTML = """

div {
border: 2px solid black;
}

"""
display(HTML(testHTML))
```
**Screenshot**
[https://imgur.com/naSsmJE](https://imgur.com/naSsmJE)

**Version Information**
[https://imgur.com/HcE0GSO](https://imgur.com/HcE0GSO)

Start by running the provided display(HTML(testHTML)) reproduction in Jupyter Notebook and inspect how the embedded style reaches the notebook UI. Done means CSS from displayed HTML no longer changes the notebook IDE styling while the displayed HTML keeps its intended styling.

Written by the indexing model from the issue text.