The modern fashion that all and anything can be identified from a photograph, including photographs of juveniles, will also simply result in a lot of incorrect records and web traffic for no good purpose. I would certainly say that the spider pictured at http://www.flickr.com/photos/mickmassie/6931647794/ 
link is indeed likely to be an Araniella species and not A. alsine. People jump to the conclusion just from the colour that an araneid must be A. alsine when plenty of garden spider Araneus diadematus can be orange for example, a large proportion of Araniella juveniles can be orange and so on. Araneus diadematus can usually be distinguished by the abdominal markings, including in juveniles, but these are also very variable and sometimes indistinct. Araniella species certainly cannot be reliably determined without microscopical examination, and even then can be difficult.
Other than the very small proportion of species where for various reasons it is safe to assume a juvenile identification, adults are a must. The only way of getting experience of juveniles and making PROVISIONAL identifications in the field or from photographs is by examining a lot of adult spiders under a microscope over a great many years and rearing juveniles through.