<a href="http://www.omsaicreche.blogspot.com" onclick="location.href='http://www.omsaivatikanoida.blogspot.com';" target="_blank">Open Two Links With One Click</a>
I tried the above codes. I could not get success in old page. Than I created a new page in blogger and types following codes... I was successful
it is working perfectly by only using html
<p><a href="#"onclick="window.open('http://google.com');window.open('http://yahoo.com');">Click to open Google and Yahoo</a></p>
it is not possible to do using only html
If you have the authority to edit the pages to be opened, you can href to 'A' page and in the A page you can put link to B page in onpageload attribute of body tag.
also you can open more than two page try this
`<a href="http://www.microsoft.com" target="_blank" onclick="window.open('http://www.google.com'); window.open('http://www.yahoo.com');">Click Here</a>`
Source: Stackoverflow.com