Thread:Project:Support desk/Standard for attributes in gallery

Hello, I would like to ask what is a standard for attributes and values in gallery tag. I noticed that e.g. values for heights works all, even the combination of them: 50, 50px, "50", "50px" (even for heights and widths 50 versus "28px"). Is there any way how attributes of that tag can be listed? I.e. which goes first? How to use showfilename? There is no example on the help page.