A month ago I purchased a new iMac desk top with Yosemite. As the weeks have gone by I'm increasingly getting messages 'Safari can't find the server' when to I try to visit my regular sites. The situation is that it will access another site straight away but won't permit the site I want. However, within a minute or two that site does become accessible. Sometimes I get the message within a site when I try to access sub page.
I would stress it's not particular sites that cause the trouble. Today I might not be able to visit a site I could yesterday whilst the site that was unavailable yesterday is today. At the moment it's a minor inconvenience because the sites do appear if I wait a minute or two and try again but I'm concerned that the situation might worsen.
A cursory look across the internet suggests that this is not an uncommon situation and some people experienced it with Yosemite's predecessors such as Mountain Lion. Various explanations and solutions seem to be proffered depending on the site visited. As I've always found PC Advisor the most helpful tech site I thought I'd asked here.
Until a month ago I've always had Windows and have never had line connection difficulties.