A selector that can be applied to any HTML element. ID should be used when designing for a single instance, such as using the id="main" attribute on an <h1> tag.

More terms you might want to know

Serial Position Effect

A phenomenon in psychology in which recalling items in a list imposes an order on the list, with the first and last items remembered best. That is, if given a list of words to remember like "dog apple tree", people will tend to recall "dog" as being at the beginning of the sentence and "tree" as being at the end of it.


The measure of how easily light passes through a material. It is a quantitative characteristic that can be represented as a number within the range of [0, 1], and in some cases [0%,100%], with lower numbers indicating higher transparency.

Crop Marks

Also called trim marks, are markings on artwork that tells the printer where to cut the page.

Font Colour

Also known as text colour, is a visible attribute of text determined by the combination of text and background colour.


PPI stands for Point Per Inch. PPI is the number of dots per inch in a printer's resolution or the number of pixels per inch in a monitor's screen resolution. The more PPI, the higher your image quality will be as it becomes sharper and clearer. The lower your PPI, the lower your image quality will be, and the more likely you'll see individual pixels in an image.

Soft Return

Also called a line break, when you want to keep the text in one paragraph and not follow it with an airy space.

Centre Aligned

A layout where all the content, mostly text, is aligned to the centre. The overall purpose of a Centre Alignment is to make it easier for users to read and scroll through content.

Placeholder Text

Text that is used to fill in a gap in a document.


A decoration technique used primarily on paper, metal, and some plastics in which ink or another printing medium is pressed into the material's surface to create a three-dimensional effect.


The last line of a paragraph following the rest, or a single line in a paragraph that is out of place with the rest.


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