The NewPageCSS extension uses the tag <css> to include a CSS in the text of the wiki page; that CSS is then put into the header of the resulting HTML, and so formats your page. If you are creating a wiki page that ends up requiring a lot of style modifiers, it's probably simpler to put them into a CSS style sheet.

Usage

<css>
table.uc {
    border-collapse: collapse;
}

.uc th {
    background-color: #f2f2f2;
    border: 1px solid black;
}

.uc td {
    border: 1px solid black;
}

.uc td.pm {
    background-color: #ffa0a0;
}
</css>

<table class="uc">

...

</table>

See also

I would like to acknowledge the author of the original extension PageCSS (Ævar Arnfjörð Bjarmason), which I have updated so it will work with current versions of MediaWiki.