Link: https://50.62.213.246/gktest/
The placeholder text and input text in the search bar will not respond to font-weight: 300; If I try font-weight: 700; the text is bold. normal = 400, light = 300, bold = 700, etc
So my question is why does the text not appear light with font-weight: 300; ?
Your link uses the https protocol.
http vs https - for a protocol agnostic reference, use //fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,600,700|Roboto:400,300,700,500,100
Basically your link uses https but you're referencing the http version of the font. So if you use https - it's a secure page, and as such, it will block non secure resources (especially from 3rd party websites), such as javascript. Or at least may display a warning, explaining that the site is trying to load non-secure content.
来源：https://stackoverflow.com/questions/20525609/font-weight-with-google-fonts-roboto-normal-400-and-bold-700-work-light-3