You can read about some of the noteworthy changes in the following articles:
Google Algorithm Changes For April: Big List Released
Google Increases Base Index Size By 15 Percent
Google Makes More Freshness Tweaks To Algorithm
Bi02sw41: Did Google Just Make Keywords Matter Less?
Google Should Now Be Much Better At Handling Misspellings
Google Tweaks Algorithm To Surface More Authoritative Results
There were over 50 changes announced for April, and 4 of them had to do
specifically with sitelinks:
- “Sub-sitelinks” in expanded sitelinks. [launch codename "thanksgiving"]
- This improvement digs deeper into megasitelinks by showing sub-sitelinks
- instead of the normal snippet.
- Better ranking of expanded sitelinks. [project codename "Megasitelinks"]
- This change improves the ranking of megasitelinks by providing a minimum
- score for the sitelink based on a score for the same URL used in general ranking.
- Sitelinks data refresh. [launch codename "Saralee-76"] Sitelinks (the links that
- appear beneath some search results and link deeper into the site) are generated
- in part by an offline process that analyzes site structure and other data to
- determine the most relevant links to show users. We’ve recently updated the
- data through our offline process. These updates happen frequently (on the order
- of weeks).
- Less snippet duplication in expanded sitelinks. [project codename "Megasitelinks"] We’ve adopted a new technique to reduce duplication in the snippets of expanded sitelinks.
the other link from the list a bit more useful though. It goes to a blog post from Google’s
Inside Search blog from last summer, talking about the evolution of sitelinks, when they
launched full-size links (with a URLs and one line of snippet text) and an increase to the
maximum number of sitelinks per query (from 8 to 12).
At that time, they also combined sitelink ranking with regular result ranking to “
yield a higher-quality list of links” for sitelinks. Preusmably, it is that aspect, which
Google considers to be “megasitelinks” as that is the code name of the change listed
in the new list, which talks about better ranking of expanded sitelinks. The change,
as noted, provides a minimum score for the sitelink based on a score for the same
URL used in general ranking.
One of the changes was a data refresh, so the sitelinks gathered should be based
on fresher information.