Any browser has it's own method to change the startup page. But since you didn't tell what browser you use, nobody can give instructions that would work with you.
There are other options, of course, like:
1. You know how to change it, but it's locked.
2. You can change it, but somehow it's changed back automatically if you reboot.
You need to tell more, I'm afraid.
Can anyone please give me instructions on how to remove www.22nd.com as my start up page?