Disagree. The best example you can find is when you browse to a web page that has an image on it, and when you mouseover the image, you get a magnifying glass. Clicking on the glass causes the picture to instantly be redisplayed at full resolution. (ignoring DPI) The smaller image was being displayed at a specified size or DPI, doesn't matter which, it was overriding the size the browser was going to display it at.
That only happens if you browse directly to an image. not to an HTML file, and the image is bigger than what will fit in the browser window. The browser scales it to fit the window. Again, DPI is ignored. ONLY the image's dimensions in pixels is considered. An image that is 2,000 pixels by 2,000 pixels at 72 DPI will behave, and display, identically to an image that is 2,000 pixels by 2,000 pixels at 300 DPI which will behave and display identically to an image that is 2,000 pixels by 2,000 pixels at 10,000,000 DPI. The browser looks at the pixel dimension of the image, looks at the pixel dimension of the window, and scales the image down to fit the window. When you click the magnifying glass, the browser scales the image up to its full pixel dimension.
I've also seen other cases where I didn't get the mag glass, and I control-clicked on an image and "open image in new window" and it opened a new window and displayed the image a great deal larger. In cases like that, no image tags apply and the image will be shown unadjusted/unscaled.
What's happening there is that the HTML on the page is scaling down the image. Say the image is 800x800 pixels. The HTML contains code that looks like
img src=theimage.jpg width=200 height=200
So the 800 by 800 pixel image is forced to be scaled down to 200 by 200 pixels. When you open the image in a new window, the browser displays it at its real size, 800 by 800 pixels.
Again, this behavior will be identical, and the result will be exactly the same, for an image that is 800 by 800 pixels at 72 dpi, an image that is 800 by 800 pixels at 300 dpi, and an image that is 800 by 800 pixels at 10,000,000 dpi. The only part that matters is the 800 by 800 pixel part.