HTML Formatting
Mark the important deadline in a sentence and write the formula CO2 with a subscript.
Understand the topic
Formatting elements communicate differences within text. strong indicates importance, em indicates stress emphasis, and mark highlights relevant text. sub and sup describe subscripts and superscripts. b and i have more specific attention or alternate-voice uses and do not automatically mean importance or emphasis. Pick the element that matches what the text means.
Worked example
<p><strong>Warning:</strong> the floor is wet.</p>
<p>Please arrive <em>before</em> noon.</p>
<p>Water is H<sub>2</sub>O. The area is 12 m<sup>2</sup>.</p>
<p>Your search matched <mark>HTML</mark>.</p>The warning is important; the arrival time carries emphasis. Subscript and superscript express notation rather than arbitrary small text.
Practice
Mark the important deadline in a sentence and write the formula CO2 with a subscript.
Show a suggested answer
<p><strong>Apply by Friday.</strong></p>
<p>Carbon dioxide: CO<sub>2</sub>.</p>Common mistake
Do not assume that making every sentence bold improves accessibility. Use emphasis selectively so genuinely important text stands out.