The writing-mode property specifies the direction in which the text is displayed. It can be used to display text vertically. Example: element { writing-mode: vertical-lr; }.

The letter-spacing property in CSS controls the space between characters (letters) in the text of an element. Example: element { letter-spacing: 2px; }.

To make text superscript in CSS, you use vertical-align: superscript;. This moves the text above the baseline, making it appear smaller and higher.

The opacity property in CSS controls the transparency of an element. Values range from 0 (fully transparent) to 1 (fully opaque). Example: element { opacity: 0.5; }.

The margin property is the shorthand for setting all four margin values (top, right, bottom, left) in a single declaration. Example: element { margin: 10px; }.

The padding property does not accept negative values. Padding defines the space around an element's content, and negative values would create undesired or incorrect layout behavior.

The font-weight property in CSS is used to define the thickness of the font. Valid values include normal, bold, lighter, and numeric values. However, thick is not a valid value. The correct value would be bold for thicker text.

The padding property is the shorthand for setting all four padding values (top, right, bottom, left) at once. Example: element { padding: 10px; }.

The text-decoration property controls the appearance of text decorations like underlines. Setting text-decoration: none; removes the underline from links (<a> elements).

The correct CSS syntax to change the background color of all <p> (paragraph) elements is p { background-color: red; }. This applies the style to all paragraphs.