Google Alerts - how does Google detect "new" content?

[inlinear]

I'm using Google Alerts for example for my domain-name.
Volume: Only the best results, How often: As-it-happens

When I was building a portal for a client I set various banners that contained a link to my site. About 4-6 weeks later Google started to send me Alerts for these pages containing the links. O.K. that I found pretty normal.

But as I receive at least 2-3 Alerts per week about the same pages from this portal now, I ask myself:
"What makes Google to consider these links as new, although these pages where they come from are for many months now online, and aren't changed?

[SeoMartin1]

it finds new content from links.... and for each site it has a "check new version and links again" time.

So if you publish every day, google usually will find your new content everyday because its spider ( googlebot) back to the site everyday.

If you publish only once per month, google will come back to your site only in 30 days and.... new content only in the next month

[inlinear]

Hi Martin,

exactly thats the point! Because I get alerts although nothing gets published or updated on these pages.

May be the pages which contain my banner and link with my domain name get new links? And when there appears a new link pointing on this page ... google detects this page again as a new "publication" and sends an alert?

[SeoMartin1]

Usually when you receive the alert is the first time google find your content... is new for google, but old for you

sitemap.xml and webmastertools can help you index all your content faster

[inlinear]

The Pages I get alerts from  have been indexed months ago. But the question remains, what exactly makes google find the link on pages "several times":which have already been indexed, and never changed since the first alert?