Images, such as photos or graphics, enhance the visual appeal of a web page. Images are defined with the <img> tag. It is empty, contains attributes only, and does not have a closing tag.
Syntax and Example
The image (img) tag allows you to grab an image file and incorporate it into the page directly.
<img src="/path/to/image" alt="Alternate Text" style="width:128px;height:128px" />
The src attribute defines the URL (web address) of the image. This can be an absolute or relative. Linking to an image on your own system is generally the best because you can't be sure an external image will still be there when the user gets to the page.
The alt attribute specifies an alternate text for the image. Alternate text information is used when the user has images turned off and by screen readers.
You can use the style attribute to specify the width and height of an image.
HTML Best Practices
Always specify the size of an image. If the size is unknown, the page will flicker while it loads.
For SEO purpose and screen readers, always use appropriate alt attribute.
New in HTML5: Figure Captions
HTML5 introduced the <figure> and <figcaption> elements. The <figure> element is used in conjunction with the <figcaption> element to mark up diagrams, illustrations, photos, images and other things. The <figcaption> element is optional and can appear before or after the content within the <figure>.
<img src="/path/to/image" alt="Alternate Text" />
<p>This is an image of something.</p>
You can now semantically associate captions with their image counterparts.
The GIF is best when you need transparency or animation. Avoid using GIF on photos, as you won't get optimal compression, and you may lose color data.
The JPG format (sometimes also called JPEG) is a relatively old format designed by the Joint Photographic Experts Group. It is most useful for photographic images, which are best suited for the JPG compression technique. However, keep in mind that JPG isn't suitable for images that require transparency. Text in JPG images tends to become difficult to read because of the lossy compression technique.
The PNG (Portable Network Graphics) is useful in most situations. Like GIF, PNG stores data without losing any information. It supports as many colors as you want. You are not limited to 256 colors like you are in GIF.