What is a Title Tag?
The title of your page is perhaps one of the most important content areas of your site for SEO. 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 Too Short" Mean?
It means a title tag that is less than 200 pixels wide when rendered with 20px Arial font.
Title length is measured by pixel width in this way because that is how it will appear on the Google SERP. There is no character limit, since different characters can have dramatically different widths. For example, "iii", "www", and "搜索量" are all three characters long, but take up very different amount of horizontal space.
Why It's Important
The title tag is one of the most important areas on your site to include keywords. If you’re using a title that's less than 200 pixels wide, it’s likely the is under-optimized since it can be difficult to fit all your targeted keywords in such a small space.
If you don't fix this issue, there's likely no penalty. It's just a potentially lost opportunity.
How to Fix
Search engines typically display the first 570px of a title (which is about 50-60 English characters). Consider utilizing the remaining space in the title to include your targeted keywords.
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 570 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