Bitmap scaling doesn't become blurry if you have enough resolution (e.g. going from 2x to 1.5x is fine). Vector scaling breaks because layout calculations don't take the pixel grid into account.
The most egregious example of this is CSS floats, where browsers have to do all sorts of hacks to ensure that percentages still add up to 100% after rounding. Otherwise fractional zoom factors cause layouts to have pixel gaps or overflow onto other pages. Fonts get around this with hinting but there's no way to hint a CSS layout.
The most egregious example of this is CSS floats, where browsers have to do all sorts of hacks to ensure that percentages still add up to 100% after rounding. Otherwise fractional zoom factors cause layouts to have pixel gaps or overflow onto other pages. Fonts get around this with hinting but there's no way to hint a CSS layout.