Generally STLL tries strives to support a subset of HTML and CSS. The set that is supported is supposed to be conforming to the specifications. If it is not it is likely a bug and needs to be fixed.

Nevertheless, the supported subset of HTML and CSS is limited to whatever is suitable for the intended usage, namely: text output in games and GUIs.

The library will be very picky, if it detects something that is not according to what it expects, it will throw an exception.

The following 2 sections will try to detail the supported subset of HTML and CSS.

HTML

The following tags are supported (but keep in mind that you have to specify proper CSS to actually see proper results

html
header, the content is ignored
body
p
h1 - h6
i, small, strong, sub, sup, q, em, code, b
ul, li
div, span
br
img (only within phrasing, no floating, image size must be specified and in pixel size)
table, td, tr, th (column sizes must be specified in colgroup tags, colspan and rowspan is supported)

All named characters and the universal named characters are supported.

Global attributes:

lang, the value is inherited by subtags, it may be used for language dependent CSS rules and it is used by the text output for language dependent shaping

CSS

The following selectors formats are supported:

selection by tag, e.g. "p"
selection by class, e.g ".framed" for tags with class="framed" attributes
selection by attribute, e.g. p[lang|=he] for paragraph tags with language attribute that starts with "he"

The following attributes are supported:

color to set text color, only #-syntax and "transparent" is supported, there is no default here, you have to set it
font-family to set a font family, the default family is "sans"
font-style, font-variant, font-weight
font-size to set the font size. There is no default here, you have to set it in a CSS rule
padding, to set box padding, only sizes in px units are supported
text-align, text_align-last to set text aligning
text-indent for indentation only px sizes
direction to set basic text direction, this influences lists (where are the bullets) and text output (left or right or last list alignment in justification)
border-width only pixel sizes
border-color only #-syntax and "transparent", when "" then the normal color attribute is used
background-color, only #-synatax and "transparent", default is transparent
text-decoration, only the underline attribute, everything else means nothing
text-shadow, multiple shadows are possible, blurr always required, set to 0 if you want none, colour also always required
border-collapse
vertical-align in table cells and only values "top", "middle", "bottom", default == top