Web fonts are files that have to be downloaded to the user’s browser, so try to limit how many different fonts are used in a design. If the bold and italic versions of a typeface are used only once or twice in a design, it may make more sense to allow the browser to create the bold or italic versions. Desktop software used to do this, applying a faux-bold or faux-italic style to a font.
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Use myfonts.com; export fonts with Bounding Box line height, NOT Best (which is the default). Bounding Box line height will ensure that the y-padding between font types is the exact same (for example using IE or Edge and text on styled buttons)