HTML Guide for left

A non-numeric value is set for the left CSS property, which requires a valid length or percentage.

The left property in CSS must be assigned a value that is a length (such as px, em, rem), a percentage (ending in %), or certain keywords like auto, inherit, initial, unset, or revert. Common mistakes include missing units (for example, using left: 10; instead of left: 10px;) or attempting to use invalid strings.

Invalid example:

<div style="position: absolute; left: 10;">
  This will trigger a validation error.
</div>

Valid example with units:

<div style="position: absolute; left: 10px;">
  This is a valid use of the left property.
</div>

Valid example using a percentage:

<div style="position: absolute; left: 50%;">
  This will position the element halfway across the container.
</div>

Valid example using a keyword:

<div style="position: absolute; left: auto;">
  This uses the auto keyword for the left property.
</div>

Always specify a valid unit, percentage, or keyword for the left property to ensure HTML and CSS validation.

A non-valid value is being assigned to the left CSS property.

The left property positions an element horizontally if it is positioned (relative, absolute, fixed, or sticky). Valid values include lengths (e.g. 10px), percentages (e.g. 50%), keywords like auto, or the value inherit. Using an unsupported value (such as X, an undefined variable, or a misspelled unit) will trigger this error.

Valid left property values:

• <length>: e.g., 10px, 2em
• <percentage>: e.g., 50%
• auto
• inherit
• initial
• unset

Invalid example:

<div style="position: absolute; left: none;">Invalid left value</div>

Valid examples:

<div style="position: absolute; left: 20px;">20 pixels from the left</div>

<div style="position: absolute; left: 50%;">Centered horizontally</div>

<div style="position: absolute; left: auto;">Let browser decide position</div>

Be sure to replace any invalid or undefined values in the left property with standards-compliant ones as above.