Wikipedia:WHENTABLE

It is recommended that be used in place of HTML tables, as they are easier to customize and maintain. A standard "" is available, by adding to the top row of the table. The powerful and useful sorting feature can be enabled by adding class="sortable" to the top row. Extreme caution should be applied if rowspan or colspan is used. It is also possible to combine classes, as in .

Much of WP:Manual of Style § Article titles, headings, and sections also pertains to table headers: Use sentence case; avoid redundantly including the subject's name in a header; do not put images in the header (including flag icons), unless this is the best way to present tabular information in a particular case; and do not use questions as headers. Title headers are often suitable places for reference citations (e.g., to source a specific row or column of data). Unlike section headings, they often begin with or consist entirely of numbers (such as model numbers, dates, version numbers, etc.). Table headers do not automatically generate link anchors the way section headings do; use the {{}} template to turn a header's text (or part of it) into an anchor.

In general, styles for tables and other block-level elements should be set using CSS classes, not with inline style attributes. This is because the site-wide CSS is more carefully tested to ensure compatibility with a wide range of browsers; it also creates a greater degree of professionalism by ensuring a consistent appearance between articles. Deviations from standard conventions are acceptable where they create a semantic distinction (for instance, the infoboxes and relating to The Simpsons use a yellow color-scheme instead of the customary mauve, to tie in with the dominant color in the series) but should not be used gratuitously.

Consideration may be given to collapsing tables which consolidate information covered in the prose.

See MOS:COLOR for information about restrained use of color in tables, to avoid creating accessibility problems for visually-impaired as well as normal vision readers.

On the other hand, overloading tables with too much detailed statistical data is against policy. Careful thought should be given to how a reader would use a table, and what level of detail is appropriate.

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Wikipedia