Horizonal screen not working

[hnmc_2526]

My iPhone 4 screen doesn't change horizonal when I turn the phone sideways.  Do you know how I can fix this?

[#2]

Double press the large button at the bottom.

Then slide the apps etc. to the right. at the end you will see the music control and at the end a box with a circular arrow. tap it and you will see portrait orentation enabled or disabled

[hnmc_2526]

That fixed it, than k you!