While you may have a good reason to write styles inline using the “style” attribute, generally it is not a good practice. In this case styles are not reusable, too specific, and the code becomes bloated and difficult to maintain. We suggest identifying common styles and including them with a style sheet.
If this is a site under development, versus a retired page of content, confirm it is an HTML5 page, using the HTML5 doctype: <!DOCTYPE html>
New HTML5 elements are not recognized by Internet Explorer versions less than 9. These browsers still have a huge market share, and it is highly recommended that you use an HTML5 shim.
This is an important and loaded checklist item. If the site is HTML5 (first line is <!DOCTYPE html>), tags like <header>, <footer> and <nav> should be used. Menu items should be marked up as an ordered list.
Common things that should be avoided are using the <br> tag for formatting, using <b> when you mean <strong>, or worse, using <b> when the content is a heading.