Images can be displayed in HTML document by using <img> tag as shown below:

Default image. Same size.
Taj Mahal

Wrong spelling. No image will get displayed. Alt text will get displayed
Taj Mahal - Wrong spelling

Image will occupy 50% width of browser. If we change width of browser the size of image will also change proportionately.
Taj Mahal - Half screen

Image will occupy 25% width of browser. If we change width of browser the size of image will also change proportionately.
Taj Mahal - Quarter screen

Image will occupy complete width of browser. If we change width of browser the size of image will also change such that its width is same as width of browser display portion.
Taj Mahal - Fit width

Image with fix width of 320 pixels. No matter what is the size of browser window, the size of image will stay same.
Taj Mahal - 320 pixels wide

Image with fix width of 160 pixels. No matter what is the size of browser window, the size of image will stay same.
Taj Mahal - 160 pixels wide

Image with fix height of 586 pixels. No matter what is the size of browser window, the size of image will stay same.
Taj Mahal - 586 pixels large

Image with disproportionate height and width.
Taj Mahal - 400 width, 400 height