What is a Title Tag?
As its name suggests, this tag includes the title or very brief summary of the content users can expect to find on the page. It's found in the head element of the HTML source.
A typical title tag:
<title>Your Source For Blue Widgets & Green Widgets | Acme Inc.</title>
The title is used in many places, but perhaps the two main areas of importance are the browser's title bar and the anchor text of your page's snippet on the SERP. Search engines give content in this area perhaps the highest weight of any content area on the page, so it's important that this area is optimized well.
What Does "Title Empty / Missing" Mean?
It means that there was no title content found on the page. This could mean one of two things - either the tag is missing completely, or it was left blank with no content (e.g. "<title></title>").
Why It's Important
Omitting the title tag on a page is a huge missed opportunity and a possible usability issue.
The title tag is perhaps the most important place on the page to put keywords for SEO. By not having a title tag on your page at all, you're missing an important opportunity to help the page rank for your targeted keywords.
Since the title is used as the anchor text for the link to your site on the SERP, search engines will have to create their own by using content on your site. Usually, titles generated by search engines are not the kind of enticing titles that users will want to click on. By not creating a title for the page, you're giving up control of this crucial element, and it could lead to a much lower click-through rate for your site.
Omitting the title tag has a negative effect on the user experience. Since it appears in the title bar of their browser, users look at the title of a page to understand what the page is about or to keep track of which page they're on if using multiple browser tabs or windows. The title tag is also used when bookmarking a site, sharing on social media sites, in your browser's history, and more. Without a title tag, these things will have to use another piece of content found on the page in its place, which may not be ideal.
How to Fix
You can fix this issue simply by adding a title tag to the page and making sure it includes a value for the content area. Follow the guidelines below for best practices.
Other Guidelines for Writing Effective Titles
Rewrite the title for each URL using your most important targeted keywords and keeping it under 570 pixels wide. Here are some other best practices for writing good titles:
Each title should be unique. Ideally, no two URLs should share the same title.
Place your most important keywords as early in the title as possible
Keep title length to 600 pixels wide, which is about 50-60 English characters
Keep your brand name or site name towards the end of the title
Titles should be natural and human-readable, not just comma-separated keyword lists
For large sites, consider writing rules to programmatically generate your page titles, but make sure these are human-readable and make sense