HTML <img> width Attribute
An image with a height and a width of 42 pixels:
The width attribute specifies the width of an image, in pixels.
Tip: Always specify both the height and width attributes for images. If height and width are set, the space required for the image is reserved when the page is loaded. However, without these attributes, the browser does not know the size of the image, and cannot reserve the appropriate space to it. The effect will be that the page layout will change during loading (while the images load).
Tip: Downsizing a large image with the height and width attributes forces a user to download the large image (even if it looks small on the page). To avoid this, rescale the image with a program before using it on a page.
Differences Between HTML 4.01 and HTML5
In HTML 4.01, the width could be defined in pixels or in % of the containing element. In HTML5, the value must be in pixels.
|pixels||The width in pixels (e.g. width="100")|
HTML <img> tag