Hello everyone I think about png size , when design websites.Which size will YOU advice to use in background picture , for example if i want to save some traffic , when user connect to my site from mobile phones and tablets ? Thank YOU Best Regards
Save bandwidth? A small repeating background would probably be optimal, if a background is needed at all. The PNG size is related to how the image was made, a big full screen image with a lower resolution can have the same byte size as a very high resolution small dimension image. A lot of sites don't use BGs at all, so that would save a lot right there on the bandwidth and load time for mobile. Is a BG needed? If so can it be a low res(PPI) image as opposed to a hi res image? It all depends on the site, it's use, and what your view point is.
BEST? That's easy... none. When bandwidth is an issue, swing an axe at the presentational crap that has NOTHING to do with what a website exists to do, deliver CONTENT to USERS. Something the massive space wasting background image asshat bullshit one typically finds on artsy-fartsy "designer" sites made by people who have zero business designing a damned thing out of their IGNORANCE over accessibility, really need a giant axe swung at them. See the endless hordes of sites that basically copy the format parodied by every ****ing bootstrap site ever! There's a reason most of the people calling themselves "designers" are either deluded artists, or outright scam artists; they don't know enough about HTML, CSS, Accessiibility, bandwidth, emissive colourspace, specifications, or any of the other things required to actually DESIGN anything. ... and that includes full size full screen background images, parallax scrolling, and all the other artsy bullshit that more often than not is a pathetic attempt to cover up for a lack of content, the idea of some marketing dipshit know knows shit about shit, or some PSD jockey spanking it on the screen in complete ignorance. More often than not it's not just a giant middle finger to speed, it's also flipping the double bird at visitors to the site who could give a flying purple fish about any of that crap and instead -- like the little old lady in the 1980's Freckle Bitches commercial -- leaves users going "WHERE'S THE BEEF!?!" Because like most artsy fartsy crap, it's fluff and filler. It's a big bun, a big fluffy bun. It's a very big bun...
I recommend 1920 x 1080 or smaller with a ratio of 16:9, which is 1.777 to 1. (Prior to May, 2014, I recommended 1440 x 900.) For making it happen, I recommend using media queries to select the appropriately sized image from a pool of 2 or 3 sizes.