This is the best practice and recommended style guide for numbers on your website:
- Use numerals, instead of spelling out the number as a word: 7 as opposed to seven
- Writing out the numbers 1-10, is a rule from writing for print
- Use commas every 3 digits (per thousand) in large numbers: 1,000 / 100,000 / 1,000,000 and so on.
Using numerals on the web is recommended because it helps readers to scan easily.