Compacting HTML code, including any inline JavaScript and CSS contained in it, can save many bytes of data and speed up downloading, parsing, and execution time.
Page Speed recommends:
Minifying HTML has the same benefits as those for minifying CSS and JS: reducing network latency, enhancing compression, and faster browser loading and execution. Moreover, HTML frequently contains inline JS code (in <script> tags) and inline CSS (in <style> tags), so it is useful to minify these as well.
Note: This rule is experimental and is currently focused on size reduction rather than strict HTML well-formedness. Future versions of the rule will also take into account correctness.