Launch putty from browser

Hi , I was trying to launch putty from browser and am using below command.

ssh://username@hostname-i-pathofthekey

but when i try this i am getting host not found error. how can i user winscp ssh protocol for launching putty

You cannot specify PuTTY command-line switches in the URL. But you can use WinSCP advanced settings URL syntax:
https://winscp.net/eng/docs/session_url#advanced

Like this:

Thanks Martin, it worked. Sameway i have tried with password but its again prompting password. Can you please help me on this also. Thanks in Advance.

ssh://username:password@hostname

That works for me.
Make sure you have the latest version of WinSCP.
Post a PuTTY event log and use Windows Task Manager to check what command-line parameters were used to launch PuTTY.

Putty Session Log:

2020-03-04 17:57:16 Looking up host "192.168.33.11" for SSH connection
2020-03-04 17:57:16 Connecting to 192.168.33.11 port 22
2020-03-04 17:57:16 We claim version: SSH-2.0-PuTTY_Release_0.72
2020-03-04 17:57:16 Remote version: SSH-2.0-OpenSSH_7.4
2020-03-04 17:57:16 Using SSH protocol version 2
2020-03-04 17:57:16 No GSSAPI security context available
2020-03-04 17:57:16 Doing ECDH key exchange with curve Curve25519 and hash SHA-256 (unaccelerated)
2020-03-04 17:57:16 Server also has ecdsa-sha2-nistp256/ssh-rsa host keys, but we don't know any of them
2020-03-04 17:57:16 Host key fingerprint is:
2020-03-04 17:57:16 ssh-ed25519 255 0e:37:b9:6c:b2:6e:9c:38:df:99:f7:4f:bd:53:d8:3f
2020-03-04 17:57:16 Initialised AES-256 SDCTR (AES-NI accelerated) outbound encryption
2020-03-04 17:57:16 Initialised HMAC-SHA-256 (unaccelerated) outbound MAC algorithm
2020-03-04 17:57:16 Initialised AES-256 SDCTR (AES-NI accelerated) inbound encryption
2020-03-04 17:57:16 Initialised HMAC-SHA-256 (unaccelerated) inbound MAC algorithm
2020-03-04 17:57:16 Using SSPI from SECUR32.DLL
2020-03-04 17:57:16 Trying gssapi-with-mic...
2020-03-04 17:57:16 Attempting GSSAPI authentication
2020-03-04 17:57:16 GSSAPI authentication request refused

i am using WINSCP Version 5.17.1 . Can you please tell me which verison you are using?

Can you post PuTTY command-line that you see in Windows Task Manager?