406 Error in Wordpress blog.

for this problem you have to contact the hosting service provider for help..

Right offhand, that most likely sounds like a mod_security issue (assuming you are using Apache). Most likely there are some character issues (IE: incomplete tags, funky characters) that mod_security thinks peculiar and dangerous.

A quick article maybe explaining it a little more in depth:
HTTP 406 Error - mod_security bites and causes problems with WordPress and Mambo | Urban Giraffe

Thanks guys.

CrazyTech, I d read this article before and d tried to disable mod_security via .htaccess but it didn't work.

<IfModule mod_security.c>
SecFilterEngine Off
SecFilterScanPOST Off
</IfModule>

I heard there is a newer version of this mod and this code doesn't work.

I just found this one
Wordpress Error 406 Fix | BlogCarta.com

hope it helps

Error 406 is from your webhost. You can try to contact your webhost
or fix it Manually if you can but prefer to choose the easiest.
Contacting the Webhost and let them fix the problem.