I have been making vector art recently and am looking into hopefully selling it either on existing websites or maybe creating my own, the website in a way would also be a portfolio and it would give me more experience in making websites and UI elements. If I were to make my own website there would be various Png versions (probably png 24) of the art at different resolutions and then a vector version.
My main question is how to save my existing vector art I have made (in Illustrator CS5) and make it available to anyone who hopefully buys it and downloads it. I was thinking I can't just let them download them the AI file because not everyone has Illustrator and if they do not everyone has the CS5 version and would a CS5 document even open in CS4 and earlier or even CS6?
When saving my existing artwork should I go back to EPS10, which is what some of the research I have done on the topic suggests and what is the process of saving as EPS10 and what are the restriction in doing so or should I just stick to illustrator and pick a version e.g. CS2 as the minimum requirement to open the art?
eps is the standard, and the process is as simple as choosing eps from the Save As menu. It's been the standard for this sort of thing (final asset delivery) for longer than I've been in the industry, is understood by basically all vector design software, and is very similar to Illustrator's native format (the original post script format eps is based on was an adobe creation, used in PDFs and in AI files).
Just don't expect artboards or anything else requiring illustrator-specific meta data to come out the same. The product - the core artwork - however, should be fine. You should make sure that anything depending on an Illustrator feature still works when expanded - but when you're producing for all versions and all vector software, this should be part of your workflow anyway.
In theory, you could use SVG as a nice modern standard that can also be displayed in browsers. Unfortunately, the way Illustrator handles SVG files is messy and non-standard, and they can't realistically replace PNG on your site as internet explorer versions before 9 (still a large % of internet users) don't understand them. But they might replace eps as the standard one day.
Tip: if selling vector artwork, make sure that there aren't any paths you think are closed that are actually left open. It's an easy, common mistake (especially if you've been drawing freehand with the pencil tool), and can cause artwork to be rejected or customers to complain - people buy vectors to work with them (generally speaking), and iunexpected open paths make them harder to work with. There are scripts that help if you have trouble. Here's an article from a stock site with more info - http://www.istockphoto.com/article_view.php?ID=578 - they recommend the free select menu plugin from Graffix