SUPER MARIO BROS

Warp to world 8:
In level 4-2, find the invincible blocks just after the
first lift by jumping up and down. Use  these invisible
blocks to punch the otherwise unreachable block. The 
punched block will reveal a most useful vine which,
upon climbing, leads to a bonus level and the wonderful
warp.

Continue:
To continue on the last world that you were on, you just
need to hold A and press Start while you are on the title
screen.