ZOHO Forms - downloaded HTML + CSS, javascript validation not working

ZOHO Forms - downloaded HTML + CSS, javascript validation not working

Hi, 
I have downloaded my form (HTML + CSS) and I just test it on my local computer, the js validation is not working, I notice before I download the HTML that show some note like:
" Input validation and Signature field will be supported only when you download the HTML/CSS code."

Please advice.

Thank you.