Although there are many formats for images, only three are supported on the Web: GIF, JPG, and PNG.
To insert an image into an HTML file, you insert a reference to the URL for that image, using the <IMG> element, as follows:
<IMG src="URL" alt="text">
Note that the <IMG> element not only identifies the URL for the image, but alternate text to display (used as pop-up text, for example, when the mouse pointer pauses over the image in a browser window). The alt attribute is required. (Click Here for a bit more about alt.)
To insert the image file logo.gif previously reference:
Absolute URL: <IMG src="http://www.grantcom.us/images/logo.gif" alt="PUBSNET logo">
Relative URL (relative to main directory): <IMG src="images/logo.gif" alt="PUBSNET logo">