When putting in ALT tags for an image that is part of a combined graphic, am I correct in saying that only the combined graphic ALT tag will be read and not, for example the three other tags that make up the graphic?
am I correct in saying that only the combined graphic ALT tag will be read
Yes. As long as the graphic elements are in fact set to combine then
there will be just one final item that is generated - and, more
importantly, one IMG tag with associated ALT element.