The answer from @ Mr.Alien is probably about what you really wanted to know. I will answer the question that you actually asked:
There is no HTML entity for a character resembling your image. This does not mean that such characters cannot be used; just the lack of certain objects.
The classic concept of an HTML entity reference is replaced by a "named character" reference in HTML5. Interpreted as related to them, the answer depends on whether your image is interpreted as "◀" U + 25C0 BLACK LEFT-POINTING TRIANGLE or as "◂" U + 25C2 BLACK LEFT-POINTING SMALL TRIANGLE. They are very similar, usually identical in shape, but of different sizes. The first has a symbol reference, ◂ , in HTML5.
However, the use of such links (other than those defined in HTML 4) is unreasonable: they have limited browser coverage, and they do not provide real benefits from the use of digital characters ◀ and ◂ (or their decimal copies) or actual characters.
Please note that these characters are only present in some fonts. This issue does not depend on how characters are entered into the document. For more information, see the Guide to Using Special Characters in HTML . (This is where CSS becomes relevant. CSS is completely irrelevant to the main issue of including a character in HTML.)