For websites it’s best to use short paragraphs made up of short sentences. When you are presenting a list of subjects, it’s a good idea to use a bullet list. If you use long paragraphs and/or sentences, you may lose your reader. However, the more likely outcome is that the reader skips the “wall of text” completely. In either case, a long paragraph, like this one, is less effective and should be broken up as much as is possible. 

It’s OK to use one sentence paragraphs.

People don’t generally read a web page the same as they read a book. Instead, they skim the page. Using bold, and italics within a sentence/paragraph helps the end user skim the text. You can also use colors (sparingly).

Below are some more tips:

• You want to have vertical spacing between each paragraph.
• You don’t typically indent at the beginning of a paragraph as you see in books.
• You don’t need to put an extra space after a period. That said, it won’t hurt anything if you are in the habit of doing it as the extra space is not shown.
• Don’t use underline as a style tool because it makes your text look like a link (one that doesn’t work). 
• When you copy text from a secondary source, like Word, the formatting is stripped out. For this reason, it’s best to wait to do the formatting until you paste it into the editor. The main exception is when you are sending text to a 3rd party to add, as that person needs to use your document as a reference point.