According to this book Professional Search Engine Optimization with ASP.NET: A Developer's Guide to SEO
by Cristian Darie, Jaimie Sirovich viewstate position does matter. There is no evidence to proof. Well known sites such as dnn, asp.net, ms are all very well know sites with thousands of visitors every hour. They are bound to be indexed by Google constantly. I belive the viewstate positioning is big help to new sites or sites that are not popular yet. I helps getting ranks faster. It  may not make any difference for dnn or asp.net. I don't think upgrading to 4.8 will lower ranking unless the page structure, keyword for the pages have changed. But I am no guru and that is just my opinion.

There are many factors for ranking. One factor is how fast the page loads and how fast a robot can crawl thru the page. Having viewstate on the top could increase time for robots crawling. Some says it may stop indexing a page. Ofcourse that will not aafect the well known sites.

I think for small sites and new sites viewstate at bottom is a big help and hope the DNN developers will take that into consideration for small site like mine.

Everything we do is a balancing act.  When discussing performance issues with Microsoft, they pointed out that moving the viewstate using our code had serious performance impacts.  After getting this feedback and researching the issue, we found that most of the advocates for moving viewstate pointed to articles that based their conclusion on the fact that DotNetNuke moved viewstate.  This becomes a catch 22.  Viewstate should be moved because some SEO guru says you should move viewstate based on the fact that DotNetNuke moves the viewstate.

So, rather than going around in an endless loop, lets try something different.  Go to the Host settings page.  Scroll down to the Performance Settings and change Page State Persistence from Page to Memory.  Now we are left with this dainty little viewstate code at the top of our page:

<input type="hidden" name="__VIEWSTATE_CACHEKEY" id="__VIEWSTATE_CACHEKEY" value="VS_keosrs45tdwuow55zem0hk25_633404779931050000" />
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="" />

So now we get a twofer - no viewstate block at the top of the page and we have a much smaller page payload.  Our pages load faster and we can stop arguing over unprovable facts about the dark arts of SEO.

Joe Brinkman wrote Everything we do is a balancing act.  When discussing performance issues with Microsoft, they pointed out that moving the viewstate using our code had serious performance impacts.  After getting this feedback and researching the issue, we found that most of the advocates for moving viewstate pointed to articles that based their conclusion on the fact that DotNetNuke moved viewstate.  This becomes a catch 22.  Viewstate should be moved because some SEO guru says you should move viewstate based on the fact that DotNetNuke moves the viewstate. So, rather than going around in an endless loop, lets try something different.  Go to the Host settings page.  Scroll down to the Performance Settings and change Page State Persistence from Page to Memory.  Now we are left with this dainty little viewstate code at the top of our page: So now we get a twofer - no viewstate block at the top of the page and we have a much smaller page payload.  Our pages load faster and we can stop arguing over unprovable facts about the dark arts of SEO.

Joe,

I think a VERY strong word of caution is needed with this setting.  There have been MANY reports in the past of issues with this setting and various modules.  I have yet to have a site that I can safely use this configuration option on.

Just my $0.02 anyway.