Recommended fonts for greatest compatibility are Arial, Verdana, Tahoma, Helvetica and Comic Sans MS.  Make sure your text is large enough to read, especially if your target audience includes seniors!

Small text blocks & white space,

Do not center align most or all text
A large amount of centered text can be difficult to read, so except for headings and maybe subheadings, left-align the majority of text across the site.

Keep width of text blocks reasonable
Wide columns of text are difficult to read, so don’t allow them to stretch across the entire screen. Keep the width below five inches if possible

Always check for errors
Check for spelling mistakes, incorrect grammar, and typos because even one error noticed can give the impression that you are uneducated, unprofessional or just not concerned with accuracy. Perfection is expected, so proof-read all pages manually before and after uploading.

Avoid clutter and “busy” backgrounds
“White space” is important so text is easier to read and it is easier to decipher different sections of the page. Make sure that the text color contrasts enough with background colors or graphics to be easily read by your entire audience, especially if that includes visually impaired people.

Be concise
Avoid too much text on main pages of site. Your home page may be fine with only a few paragraphs worth of text, as long as you cover the main points of your site. It is better to have more short pages than fewer long pages that can feel like more work to read through, as long as you keep in mind an approximate minimum of 300 words to give the search engines something to chew on. (each page of this book contains about 350 words) Main pages can direct visitors to more detailed pages.

Make it easy to skim
I repeat: Use lots of subheadings and short paragraphs. Get ideas across quickly. If you are providing more details, put them farther down on page or give them a page of their own for those who are interested.

Many more ideas in website tips eBook!