скачки по посещаемости по ключу. Возможные причины?

Такое же было - пик на 15 августа и потом спад до прежднего уровня трафика - скорее всего или внедряли или же тестировали какой то алгоритм поиска.

спасибо, я тоже думаю что скорее тестирование гуглом новых алгоритмов, но вдруг есть какая-то другая причина?

такая же история - 15, 16го увеличение, потом спад до прежнего.

Я думаю связано с этим http://analytics.blogspot.com/2011/08/update-to-sessions-in-google-analytics.html

но не понятно почему снова начало по старому считать.

как раз понятно почему стало считать по старому, по ссылке, приведенной выше написано:

Update 8/17/2011 2:10 PM PST:

We identified an issue responsible for unexpected traffic changes following our recent update to how sessions are defined in Google Analytics. A fix was released at 2pm PST Tuesday August 16th.

The issue affected some sites using the following configurations:

1. If a user comes to a customer’s site with a space in some part of their traffic source data, then revisit the same landing page during that session by refreshing the page or later pressing the back button, a new session will be created for every hit to that page. (Clicking a link elsewhere on the site that leads back to the page should not matter.)

2. Google Analytics implementations using multiple trackers (an unsupported configuration) are also affected when a space is included in the traffic source data. These sites will see fewer visits from new visitors, and more visits from returning visitors (with some variation due to different implementations).

Again, a fix for this issue was released yesterday. Please let us know if you continue to see unexpected traffic changes. We apologize for the inconvenience and thank you for your patience and continued support.

Posted by Trevor Claiborne, Google Analytics Team