Which format of digital photo is used for websites ?

JPEG (Joint Photographic Experts Group) or the JPG was the ideal format for placing digital images on a website.
Now the PNG is also a good solution but for best results PNG32 is advised.
As far as .GIF is concerned, it is not suitable for photographic images, as it has limited number of colors.
If you will convert any comprehensive color map (JPG) image in .gif you'll notice that tones and gradients will be converted into the color stripes, also sometime the edges could also get rough.
Use .GIF when you have specific number of colors or I should say the static colors and specially when you need transparency of one or more than one colors.
Hope this would be helpful.

Portable Network Graphics (PNG) for photos and Graphic Interchange Formats (GIF) for vector images or for flash videos.. jpeg? that could be heavy...

Jpeg seems to the standard thought png and gif are now common place and supported by new browsers

Jpeg, GiF, Bitmap

I think both JPEG or PNG are best for photos using in website.

The best format determine what you want to use it for,.
Imagine without white background, then we will talk about .png extension but the extension is too heavy.
But, the best option when you are not taking background into consideration, then jpeg, jpg is the best and is not heavy at all

For websites png images are used.
Please use png image while designing your site.

GIF, JPEG Formats for background images, PNG for transparent Background images and SVG is new file format that will be best format in future If people will understand that.
Hope your answer

Jpg is most common since long time now PNG enter and got a good place but still not supported by old browsers.
gif was used for animated but now a days css has beat this...

its a simple thing to decide when it comes to choosing what format to use when it comes to using images on websites.
This could be a bit complicated too...so read on carefully.
GIF & PNG 8 : it has limited colors to which varies from 8 - 256 which means if you have only 2-3 colors on an image, lets say a logo...
I'd suggest you use a GIF image as it will compress the image to its maximum with the best quality, try and (save for web in photoshop) you will notice it will heavier than GIF / PNG formats with less quality.
JPG : Widely used format for images which are of many colors, more than 256 (maximum limit of PNG 8 and GIF Formats) , photographs, stock images and so forth should be saved as JPG format.
PNG 24 : We've had fair share of problems with this format for a while but now it is compatible to all the latest browsers, why we use PNG 24? to save transparency, lets say you have a shadow on an image and you are not sure what will be the background color of the page where you will place that image, you create a transparent image in photoshop and set it to png24, it will maintain the transparency throughout the webpage...does not matter which color you use as the base color of the webpage background...so if you are are looking to save a cut out image ( anything other than a square, rectangle ) and want to save the transparency, use PNG...sure it will be bit heavier but compression is amazing as compared to the quality.
Hope it helps you choose the best out of the lot.
:)

GIF , PNG , JPEG