change flex-basis value main-size to the new content syntax. add comment to clarify that align-items, align-self, and justify-self are defined in the Box Alignment spec, which supersedes Flexbox
change flex-basis value main-size to the new content syntax. add comment to clarify that align-items, align-self, and justify-self are defined in the Box Alignment spec, which supersedes Flexbox

y0ssar1an/CSS3