[AccessD] OT Question that will be simple for those that know

Within many web pages there is starting to appear a piece of code which is
curious. It looks like encrypted imbedded coding created by some obfuscating
tool. 

The block starts like 'value="dDwtNjIxMjI0NzQwO3Q8O2w8aTwwPjtpP.... and so
on for, sometime 1000 plus characters. I would look it up on the internet
but do not know even how to describe it.

Is this the result of an obfuscating process for ASPX pages? Yes, I am
designing in ASP.Net and no, I have never run across this before. (The
disadvantages of being self-taught.)

TIA
Jim