These 2 articles explain input tag number validation methods.
Previous number validation methods had some limitations and were not fit in 100% case but these methods were 100% satisfied with the requirement.
https://stackoverflow.com/questions/469357/html-text-input-allows-only-numeric-input
https://stackoverflow.com/questions/995183/how-to-allow-only-numeric-0-9-in-html-inputbox-using-jquery/995193#995193
