Building a website can be tricky. One of the hardest bits to get right seems so simple: typography. There are some important things to keep in mind when choosing your text.
Do’s
Establish a hierarchy. Use uniform fonts or styles for headlines, subheads and body text. Don’t mix and match.
Use appropriate fonts. Choose the right font for your text. Stay away from things like Comic Sans. Also, sans serif fonts read easier as body text.
Minimize clutter. Give your text room to breathe. Don’t condense it too much and make sure it has some margins.
Limit paragraph length. Keep your paragraphs concise. 40-60 words will suffice. Large paragraphs deter readers.
Don’ts
Use small text. Keep the font size about 12 point. Anything smaller can be difficult for some to read.
Use many fonts. Remember, you want a uniform hierarchy. Don’t have more than three or four fonts per page (including headline, subhead, body and navigation text). Aim for three.
USE ALL CAPS! Seriously, don’t. It looks bad, reads bad and can imply a negative tone.
Center it. You can center chunks of text here and there, if you want it to stick out. But, try to avoid anything other than a left justified script.
Via: http://www.webdesignerdepot.com/2013/03/serif-vs-sans-the-final-battle/
http://www.webdesignerdepot.com/2013/05/dos-and-donts-of-typography/