According to this Google Blog Post:
Google has removed one of the link-related signals of what the topic of a page is
. Understandably they didn't say which signal it was:
Link evaluation. We often use characteristics of links to help us figure out the topic of a linked page. We have changed the way in which we evaluate links; in particular, we are turning off a method of link analysis that we used for several years. We often rearchitect or turn off parts of our scoring in order to keep our system maintainable, clean and understandable.
So what are the signals related to the topic of the linked page? Here are some suggestions. Feel free to add more. Title Tag
The title tag is a signal of what a web page is generally about. The title tag has been used to help identify the meaning of a linked page from the general theme of the page linking to it. The title tag is a signal of the general theme of a web page. The topic of a link can vary from a side topic to a more granular or a completely off topic meaning. Surrounding Text
This establishes the context of a link, thus helping to define what the linked web page is about. This also helps identify if a link is paid for or is associated with a donation. Position of a link
Where a link is located is an important signal. A link in the footer is presumed to be less important than a link within the body of a web page. Navigational links are presumed to be depreciated according to a set amount, perhaps more than outbound links but just a fraction of a normal non-depreciated link. HTML signals related to weighting of a link
These might include Heading Tags
[w3.org], bold, italics, capitalization and font size
[webmasterworld.com] as factors for assigning greater weight to a link. Font size is an interesting candidate for depreciation. Here is what the orignal Google Paper says about Big Fonts:
Aside from PageRank and the use of anchor text, Google has several other features... Google keeps track of some visual presentation details such as font size of words. Words in a larger or bolder font are weighted higher than other words.
[edited by: martinibuster at 9:46 pm (utc) on Feb 28, 2012]