Sorry, but this is not true. Please do a search on this forum as I cannot go on repeating and repeating this:
Images are remembered by comps as bitmaps. A bitmap is a kind of mosaic, and every building block is called a pixel. What a puter remembers for every pixel is, amongst other data, the amount of each colour and its place in the mosaic.
A pixel has no fixed dimensions. Your operating system, with the help of your graphics card decides how many pixels you can see on your monitor. For example 640x480, 800x600, 1280x960 etc. If you have, say 800x600, you will not be able to see an image of 801 pixels wide without scrolling horizontally. But ANY image that is 799 pixels wide, will be fully visible. Whether there are 72 pixels in an inch or 1254.
Then why are there so many people who still write in books that you need 72 pixels per inch for the web? Because they all copy one-another. The origin of this 72 can be found in the world of print. When DPI (desktop publishing) started, professional printers were rather reluctant because their trade is several centuries old, and they were used to their own way of measuring things. And they worked with a system of points as units. (In Photoshop, you can still choose under preferences whether you want to use the old system, or the simplified one (exactly 72 dots in an inch). This is only used for printing, never for the web. The sole intention is that you see on the monitor approximately the same size as what will be printed.
To summarize:
If you have, say, and image of 360x720 pixels, you can see it without scrolling on your monitor if the monitor can display 360x720 pixels or more.
When it is set at 72dpi or ppi, its printed size will be 5x10 inch, which will approximately be the size you see it on the monitor.
When it is set at 144dpi or ppi, its printed size will be 2,5x5 inch, or only one quarter of what you see on a monitor.
So if you want to annoy people, or prevent most downloaders to print your web images, set them at 720dpi or ppi or even more. The printed result will be less than a thumbnail. Only those who know, and have the app (like PS) can do something about this.