A hidden location which can be accessed by going out of bounds in the overworld.
There is a lute outside of the house if you don’t already have one.

Error sells Boots of Speed for 500 rupees.
Boots of Speed allows you to move as if you were playinged in fixed-beat mode.
Prior to version 1.2 Boots of Speed weren’t limited to the fixed-beat speed, instead allowing you to move as fast as you wanted.

After purchasing the boots, they will never re-appear on the save file again.
However, each out of bounds screen on the overworld has its own instance of Error’s House.
Meaning that if you can get out of bounds at multiple locations, you’re able to purchase multiple Boots of Speed.

Dungeon & Puzzle Mode

It is possible to reach Error’s House in these modes by wrong warping.
Wrong warping inside of a dungeon tries to place you outside at its entrance.
These modes do not have an entrance, so you’re sent to overworld screen 0,0, which is Error’s House.
Presumably because the modes do not generate an overworld at all, so all screens would be Error’s House.

As it requires a game over, the only way to obtain enough rupees to buy Boots of Speed is by using 9 Scroll of Need, ruling out Permadeath.
You must then get Ring of Charisma from the scroll, and after filling all 4 slots, use the remaining 5 scrolls to get Riches 5 times, totalling 250 rupees.

This can however be used to obtain the Lute in Dungeon Mode.
Using the Lute in Dungeon Mode puts you back at the same location as a Game Over / Save & Quit.
Getting the Lute this way in Puzzle mode does not do anything special, the Lute chest will still give the Lute.

This can also be done in Permadeath.