Bandwidth

[Michael]

If, for example, I have a web page of 10k and it includes a graphic of 20k, then when I download the page I have used 30k of bandwidth. No problem so far!

If I then load another page of 10k which includes the SAME 20k graphic, how much bandwidth will I have used to display the second page?

Will it be 30k? 10k + 20k
Will it be 10k? Because the graphic is cached
Or does it depend on my host?
Or even my browser setting?

[Michael]

Dummy reply to get me back to the top of the list!

[HarryW]

It depends on the client who is requesting the page. If they have cached it then assuming both images are the same file - not just copies - they won't download it a second time

To abstract from all the TCP/IP and HTTP jiggery-pokery, this is what happens:

Client requests a page from the server.
Server responds by delivering page (pure HTML text).
Client's browser parses HTML.
Any images or similar objects (.js files, style sheets etc) in the HTML are noted.
Client's cache is checked for the necessary files.
Any files not present are requested from the server individually.
Server delivers each file as it receives the requests.

So if you design your website wisely and cut out duplicate files you should, in your example, only deliver 40k for the 2 pages. If you have a seperate copy of the image for each page then it will be 60k.