What an anchor should be like
Google’s recommendations for links say that anchor text should be descriptive, reasonably short, and related to the surrounding text. A simple check: read only the link text. If it is clear where the link leads, the anchor works. “More details,” “here,” and “via the link” do not pass this check.
When an anchor does not work
If a phrase has to be rewritten to fit the entire keyword query into the link, the anchor is over-optimized. Google explicitly advises against forcing keywords into link text.
- Empty link with no text: Google may then rely only on the title, but that is a fallback option
- A keyword inserted into a sentence where it sounds unnatural
- Links placed right next to each other without explanatory text
What this means in practice
A page can be linked to using different wording: its exact title, the title with a qualifier, or a question. For an image link, the alt attribute serves as the anchor, so it should be filled in with a meaningful description.