I've been seeing people having trouble with booting into Gateway, and this guide will help you ensure an always 100% clean boot.
Set up Steps:
1. Turn Wifi Off
2. Boot up your 3DS
4. Open Internet Browser
5. Make a new bookmark for http://go.gateway-3ds.com
6. Clear history and cookies
7. Go back to Tools where bookmarks are, the page should be blank behind
8. Quit Internet Browser and reopen, the page should be blank and the 3DS will have saved this state.
9. Turn back Wifi and turn your console off.
Once you set that up, you can keep your wifi on, and you can follow this so you can have a clean launch every time so you don't get anymore errors:
Launch Steps:
1. Boot your 3DS
2. Quickly launch into Internet Browser and open the Gateway bookmark
3. The page will load just in time for the internet to connect, so it'll never visit another page to fill with cookies or history so you won't get the error anymore.
4. Profit.
OR
You do NOT have to keep clearing the cookies and history for this. Just be fast to open the bookmark and have a clean tab behind.
Set up Steps:
1. Turn Wifi Off
2. Boot up your 3DS
4. Open Internet Browser
5. Make a new bookmark for http://go.gateway-3ds.com
6. Clear history and cookies
7. Go back to Tools where bookmarks are, the page should be blank behind
8. Quit Internet Browser and reopen, the page should be blank and the 3DS will have saved this state.
9. Turn back Wifi and turn your console off.
Once you set that up, you can keep your wifi on, and you can follow this so you can have a clean launch every time so you don't get anymore errors:
Launch Steps:
1. Boot your 3DS
2. Quickly launch into Internet Browser and open the Gateway bookmark
3. The page will load just in time for the internet to connect, so it'll never visit another page to fill with cookies or history so you won't get the error anymore.
4. Profit.
OR
You do NOT have to keep clearing the cookies and history for this. Just be fast to open the bookmark and have a clean tab behind.