Use Screen Resolution
Save your graphic at a resolution appropriate for screen display
You readers are going to be viewing your pages&3151;and the graphics within themon a computer monitor. Monitors typically display data at 72 dpi. Therefore, save your files at 72 dpi.
If you are using graphics files which were originally created for print media, they are typically saved at a higher resolution. If you use a larger resolution one of two things will happen: if you've specified the image size in your image tag, the extra data will just be thrown away but your readers will get to experience the joy of a long download time. If the image size isn't specified, all that data will display and you'll end up with a huge image on the screen.
So forget the print rules and stick to the lower resolutionyou'll get the same quality, far, far smaller files, and no size surprises.
|Original physical size = 1.68 x .96 inches
Original resolution = 150dpi
Number of pixels = 252 x 144
Physical size on a Web page = 3.5 x 2 inches
This image increases to more than twice its original size because the resolution is too high.
||Original physical size = 1.68 x .96 inches|
Original resolution = 72dpi
Number of pixels = 121 x 69
Physical size on a Web page = 1.68 x .96 inches
This image is the right size because the resolution is 72dpi.