Yeah, I just tried it, but just like you nothing happens after I paste everything. 
Anyway if you're still looking for online verifier try this http://www.coinig.com/
Anyway if you're still looking for online verifier try this http://www.coinig.com/Thanks but this checker seems to be poorly written. The "too often to be seen" error of a form field with too view signs allowed i guess. Signature messages arent restricted to 250 signs as far as i know. But this script complains because i use more signs than that.
And other? Seems i need a replacement as suggestion for easy check of signatures.