What kind of image could be in the source of tag?

Question

Sample:

 <img src="smiley.gif" alt="Smiley face" width="42" height="42">

What kind of images could I use as resources (gif, .... ?) Are there any limitations?

Answer 1

According to MDN:

The HTML standard doesn't give a list of image formats that must be supported, so each user agent supports a different set of formats. Gecko supports:

JPEG
GIF, including animated GIFs
PNG
APNG
SVG
BMP
BMP ICO
PNG ICO

The W3 and WHATWG go on to say:

...images can be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page vector documents (single-page PDFs, XML files with an SVG root element), animated bitmaps (APNGs, animated GIFs), animated vector graphics (XML files with an SVG root element that use declarative SMIL animation), and so forth. However, these definitions preclude SVG files with script, multipage PDF files, interactive MNG files, HTML documents, plain text documents, and so forth.