Depends on the browser.
Try it with yours (below).
Here is a practice web page.
Play with some of the character formatting tags.
"No, no. No crime," said Sherlock Holmes, laughing.
"Only one of those whimsical little incidents which will
happen when you have four million human beings all
jostling each other within the space of a few square
miles. Amid the action and reaction of so
dense a swarm of humanity, every possible
combination of events may be expected to take place,
and many a little problem will be presented
which may be striking and bizarre without being criminal.
We have already had expericnce of such."
Insert some character formatting tags, then
to see what the HTML does.
Can you start a section with <em> and end it with </i> ?