Can't upload webpages

Hi, I'm trying to update our website which I haven't done in a while so it's not the freshest in my memory. I would drag a webpage accross and it suggests that I copy and replace as it already exists, the webpage then goes into the transfer queue and just stays there without uploading, the status says "retry at 4pm" and just continues to retry. This only happens with the webpages, the other photos etc worked. this is what comes up :
[16:01:33] STOR Boattips.html
[16:01:33] 550 Boattips.html: Access is denied.
[16:01:33] Transfer failed.
[16:01:33] Operation End
Also when I try to delete a webpage it comes up with:
[16:13:19] 550 Boattips.html: Access is denied.
Sorry if this is obvious buit I'm just new to this, it would be great if I could get some help.
Thanks, Justine

Insufficient privileges. Contact the web hosting provider.