When working with any area of the system that lets you directly edit HTML and CSS code (generally in the content editor when you click the Source.. button), we only support certain tags. Here are all supported HTML tags and their associated attributes + protocols in the CMS. When you click Save after editing content, the CMS content sanitizer strips any tags not found in this list, including script tags. Note that style and class attributes are included for all tags.
href, title, target, id, name
ftp, http, https, mailto
allowfullscreen, frameborder, height, width, src
align, alt, height, src, title, width
http, https, data
summary, width, border, cellspacing, cellpadding, align
abbr, axis, colspan, rowspan, width
abbr, axis, colspan, rowspan, scope, width
CSS rule-sets are scoped to make sure they only affect the associated content. The way they get scoped is that rule-set selectors are prefixed with the name of the content.
Local CSS at-rules are excluded from the above scoping. For now, the only supported local at-rule is @media.
@font-face, @keyframe, @charset, and @document are not supported as these are global at-rules. Using them without special handling may cause conflicts with other components and also override CMS internal at-rules.