HTML Guide for empty string
The for attribute on a label element can’t be an empty string. This attribute is intended to specify which form element a label is associated with, and it must reference the ID of an existing form element. An empty string is neither a valid ID nor a meaningful association.
Explanation
- Invalid HTML: <label for=""></label>
The for attribute expects the value to be the ID of a form element, such as an input, textarea, select, etc.
How to Fix
- Identify the Form Element: Find the form element (input, textarea, select, etc.) that the label is supposed to be associated with.
- Assign an ID to the Form Element: Ensure the form element has a unique ID.
- Modify the Label’s for Attribute: Set the for attribute of the label to match the ID of the form element.
Example
Before Fix
<form>
<label for="">Username:</label>
<input type="text" name="username">
</form>
After Fix
<form>
<label for="username">Username:</label>
<input type="text" id="username" name="username">
</form>
IDs for HTML elements can’t be blank.
An empty string for the min attribute on an input element is invalid; it must be a valid number.
The min attribute specifies the minimum value an <input> element can accept when using types such as number, range, date, or datetime-local. According to the HTML specification, the value for min must be a valid floating point number (or a valid date/time string for date inputs). Setting min="" (an empty string) is invalid and will trigger validator errors.
HTML examples
Invalid usage:
<input type="number" min="" max="10">
Valid usage (set min to a specific number, or omit it if no minimum is required):
<input type="number" min="0" max="10">
or, if no minimum restriction is needed:
<input type="number" max="10">
Always provide a valid number for min or remove the attribute entirely if a minimum is not needed.
The attributes width and height of <iframe> elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.
The attributes width and height of <img> elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.