I have a splash page where a transparent PNG will be crucial to the look...overlaying much of the left area. I'm concerned that not all browsers or computers will display it properly. If not, I'll find another way. Will users consistently see a transparent PNG these days? (edit: On modern browsers)
PNG transparency comes in two forms... palette and alpha. Alpha transparency is the one that has 'problems' -- in IE6/earlier ONLY. Worrying that someone might *OH NOES* not get a transparency in a TWELVE YEAR OLD browser is a bit silly... if someone can't join us in this century, they should get what's coming to them. That's NOT to say your site shouldn't work, but on anything that old they should be used to everything looking like arse by now. I dislike alpha for a whole host of other reasons -- biggest of which is the 25% increase in filesize and poor compression rates... meaning that for anything larger than 128x128 the file often ends up larger than I'd allow for an entire page on a site -- that's HTML + CSS + SCRIPTS + IMAGES! Palette transparency is what I prefer to use -- it means you have to reduce the color depth to 8 bits or less, and choose one solid color to be transparent from the 256 possible colors you get. If you can pre-composite (render it over the final background and clip it) the image that is one possible way of handling it. Another is to use a method called 'close-enough anti-aliasing' where you render it over a median color and use a flood-fill to strip all but the oddball pixels. It will look funny on it's own, but when rendered over the final background it's "so close as to make no never mind". Apart from that without seeing what it is you are trying to do, that leaves most of us operating in the dark. Though... splash page? REALLY? are you going to have auto-playing music, GIF animated backgrounds, and every other item from the "top ten list of how not to build a website" to go with that? Unless your plan is to do that for age verification, just say no to the splash page.