Sprites, repeat background image effects, svg/base64, pseudo element/selectors that eliminate doc. markup, etc. Do these really make a difference in the speed of a site, mobile site?

There are so many blogs and large, static pages around, it seems contradictory (for use of a better word), whether I use one div or three to make a module, or use a sprite or background image, in terms of the user experience, not semantics.

Thanks for any real world opinions.