"You want mobile notifications? Sure, but not on mobile Safari." You can do this with PhoneGap. "Multiple line ellipsis? Sure, but only on webkit." Okay, yeah, this sucks. "Consistent rendering size across browsers? Just fuck off." This is probably your fault. "We fix a layout bug on Safari and break something on Edge." This is probably your fault. "We change font size on Chrome and now all you can see on Firefox is…
As someone who has spent an embarrassing amount of time debugging kerning differences, line spacing, and obscure letter size differences across IE/Firefox/Chrome I can enthusiastically say, it might be his fault but I doubt it. Different browsers do things differently and in cases where things must be the same, this is an expensive and time-consuming problem.