Will High sierra work on my 2008 iMac machine ?
Back up your data, check your applications for compatibility, and click on El Capitan. Alternatively, switch to a product such as Firefox.
High Sierra isn't compatible with that model.
Believe El Capitan is the last version this computer Qualifies to run IF it is the last iMac of 2008 Model.
No High Sierra will not work on a 2008 iMac, El Capitan is the last OS X you can install
on this mac, you will probably have the same problems with Safari in El Capitan
as you are having at the moment in Mac OS X Yosemite.
"I have 10.10 Yosemite the Safari Browser that has worked for most sites. However I can not get updates now. Are there any options?"
Upgrade to a newer device.