Meta description is missing
This means that the URL in question does not have a meta description present in the HTML.
Why is this important?
The meta description is considered important to help users quickly understand what content they can expect to find on the page, when clicking through from the search engine results page. Well written meta descriptions typically achieve a better click-through-rate.
If the meta description is missing, this represents a missed optimization opportunity. Furthermore, this means that search engines will write the meta description for you, sometimes with pretty disastrous results (example below shows a page on our site with no meta description set...).
What does the Hint check?
This Hint will trigger for any internal URL that has no meta description in the <head>.
Why is this Hint marked 'Advisory'?
In Sitebulb, this Hint is Advisory, as it does not represent a clear issue. Meta descriptions have no impact on SEO, however they do have an impact on CTR from search results, so in general it is a good idea to set them.
However, in some situations, or for certain sets of pages, you may feel that it is not a good use of resources to write a meta description for every single page.