Use the WebCityPages Editing Tool to create new or edit existing cpor webpages. It's simple to contribute content; just use the word editor that pops up when you enter your password. If you want to do more, you have the option to write HTML by clicking on the "Source" button.
What to write/style guidelines: Your webpage could be something like a Wikipedia article, but SourceWatch is a better model. Whereas Wikipedia demands
neutral point of view (often a point of major contention) ; Sourcewatch encourages authors to have a point of view and make an implicit argument as to why a topic is important. It's standard is
fair, accurate and fully sourced. In either case, it's expected that every piece of information have an external, verifiable source.
Length: Webpages should be short and to the point, but if you're inspired you can do a series (or web) of pages.
Beyond the text: Pics, videos, graphics and other illustrations are all good. The more creative and aesthetic the better. You want visitors to see what you have to say and appreciate your work. Basic pics and graphics are fairly easy to add through the WebCityPages editor . Other features are more complicated. Your can look at some other pages to see what we've done and copy some of those formatting features.
In general, I have learned HTML by copying code from pages that I like, and making limited adjustments as strictly necessary, using sites such as w3schools to identify HTML tags and to learn other aspects of basic web programming. Although I'm debilitatingly perfectionist in much of life, I try hard to on web work to accept anything remotely good enough, especially format-wise, so as not to consume every free waking hour and then some. That said, I have picked up quite a bit programming in this fashion.
I am regularly working on improving layout and format one thing at a time, with a wish list on the back burner. Feel free to add to the list, comment on its entries, or better yet, suggest a way to do it.
 Wikipedia has become one of the most-read websites on the planet, but it is vulnerable to manipulation though anonymous edits and Neutral point of view demands even when some points of view are disingenuous.