[El Forum]

[eluser]InsiteFX[/eluser]
IE converts the under score to a chr (9) character dig deeper.

And if I have an under score in my cookie name my sessions no longer work!

After removing the under score then the sessions will work.

Cookie name with under score

[El Forum]

[eluser]Narf[/eluser]
[quote author="InsiteFX" date="1413841943"]IE converts the under score to a chr (9) character dig deeper.

And if I have an under score in my cookie name my sessions no longer work!

After removing the under score then the sessions will work.
[/quote]

Add two.
Seriously, if you've got issues with an added underscore, it's likely due to a collision. Even if IE sends the character url-encoded, HTTP servers will decode it and still recognize it properly.

I'll say this again: the very link that you gave sends cookies with underscores; microsoft.com does too.