<i> be used instead of
<em>? if so, always or only on specific situations?
The short answer is that it’s a matter of semantics.
<i> is mostly for presentation. For example, if you had a book title, you might use
<i> tag to make the title in italics.
<em> will be interpreted as actual emphasis. For example, if you wish to say “That is your bag.” (with the emphasis on “your”, obviously) you would use
<em>. It matters because a screen-reading program such as might be used by a vision-impaired person will not read anything inside an
<i> tag with any emphasis, since
<i> is merely for visual appearance.
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Why does seem the same as ?