Tell me, please, what could be the matter. In all browsers everything is displayed normally without an error, in FireFox the same font is not used, and in the debugger the error:
downloadable font: cmap: unexpected range shift (3! = 4) (font-family: "AGHelveticaCyr" style: normal weight: normal stretch: normal src index: 0) source: file: /// C: / Users / SkyWay / Desktop /% D1% 81% D0% B0% D0% B9% D1% 82-ver1% 20-% 20% D0% BA% D0% BE% D0% BF% D0% B8% D1% 8F /% D1% 81 % D0% B0% D0% B9% D1% 82 / fonts / AGHelveticaCyr.ttf style.css
downloadable font: cmap: failed to parse table (font-family: "AGHelveticaCyr" style: normal weight: normal stretch: normal src index: 0) source: file: /// C: / Users / SkyWay / Desktop /% D1% 81% D0% B0% D0% B9% D1% 82-ver1% 20-% 20% D0% BA% D0% BE% D0% BF% D0% B8% D1% 8F /% D1% 81% D0% B0% D0% B9% D1% 82 / fonts / AGHelveticaCyr.ttf style.css
downloadable font: rejected by sanitizer (font-family:"AGHelveticaCyr" style: normal weight: normal stretch: normal src index: 0) source: file: /// C: / Users / SkyWay / Desktop /% D1% 81% D0% B0% D0% B9% D1% 82- ver1% 20% 20% D0% BA% D0% BE% D0% BF% D0% B8% D1% 8F /% D1% 81% D0% B0% D0% B9% D1% 82 / fonts / AGHelveticaCyr.ttf
Here is my font download and usage code: http://jsfiddle.net/dudkj7sf/