Help:Editing
iGEM's websites are based on MediaWiki. You can read the general MediaWiki page about how to edit.
Most of our pages use HTML, rather than MediaWiki markup. To use HTML on a MediaWiki page, put <html> ... </html> tags around your page content.
W3Schools has many tutorials and references for HTML, CSS, JavaScript, and other languages that are commonly used to make webpages.