frequent error message perplexed

[keepingup]

In my office on a three year old iMac I often receive the error message:

"You are not connected to the internet
This page can't be displayed because your computer is offline"

However, my iPad, iPhone and MBA never receive this message when on the same wifi. It's extremely annoying and requires me to twiddle my thumbs for a few minutes, then it works. I've tried rebooting the wifi and the computer but it still occurs.

I have written to Apple but received no response.

Does anyone have any knowledge about this? Thanks in advance.

 

[carl201167]

Hmmm this could be a world of things. First thing: are you up to date on all software?

 

[keepingup]

thanks for responding. Yes, all software is as up to date as allowed for a few years old iMac. it's driving me crazy.