| A WORD OF CAUTION |
| A number of search engines feature “pay for placement.”
That means that
the results that rank the highest―those that you see first―are there
because those sites have paid to come up first.
Google, for
example, has paid ads on the right side of the results screen, but it may
also place "sponsored links" (more paid ads) on top of the other results of a search.
In Google these are clearly labeled as “sponsored.” However, some of the more
unscrupulous engines either omit any kind of warning or
give warnings that are very difficult to understand. If you learn
that a search engine does this, avoid it like the plague. |
|
 |
Module 4: Effective Searching on the Web
Still More about Search Engines
 Spiders crawling the
web? Please elaborate!
-
The spider program reviews pages on the
web, following links from one page to another, and then
stores the pages and indexes them (classifies them by
words contained and subjects involved). But some
pages are not linked to other pages, so not all pages get
found by the spiders. (See the pink box to the
left for more information.)
-
After a spider retrieves a page, another
program in the search engine indexes it. That is,
the program examines a variety of aspects to determine
the subject(s) of the page, including but not limited to:
-
the position of words in the page (e.g.,
in the title, the URL, the first paragraph, etc.)
-
the order of the words
-
the number of occurrences of words
-
links in the
page
Based on these factors, a link
to the page is put in the appropriate area of an index,
or list of subjects. Then when you search, you
actually search the index, which calls up the
appropriate links to pages on the Internet.
But more than number of occurrences of
words and their positions is involved. Pages are
also ranked in various ways.
Google, for example,
employs a particular
 algorithm for ranking pages called
"PageRank." This algorithm generally counts the
number of other pages that link to a particular Webpage. If page A has 26 pages linking to it, and
page B has 23, all other things being equal, page A's PageRank is higher.
Still another factor is involved in PageRank. How
choosy are the pages that link to page A and page B?
If the 23 pages that link to page B have few outgoing
links--that
is, they are very particular in linking to
other pages--that raises page B's PageRank.
Conversely, if the pages linking to page A have scads of
links to other pages also, they are treated as not very
discriminating and page A's PageRank sinks.
Again, all other things being equal, the higher the PageRank of a Webpage, the higher
on the list of results is
Google's link to the page.
Now we're ready for
another look at how
Google
answered the question about the blue sky. And then
we'll discuss techniques for getting the best results out of
search engines. |
|
