Header code won't update!

Hello,

I’m building a wordpress site for my friends and I am having a crazy problem (I might be missing something but have gone through everything I can think of):

My header file includes a large logo and three social network links. I changed some of the code (made a ul, smaller images) and then re-uploaded the new header file. The changes I made do not appear on the site, it seems like the old version is still there.

I made sure it updated (matched file size) and still nothing. I made sure I got the theme folder right: I did.

So I just deleted the header file within the online theme folder to see if it would disappear on the site: it’s still there.

How is the header still appearing if I deleted it from the theme folder?

Why can’t I make changes?

If anyone can help I would be very grateful!

Thanks

Mike