Why doesn't my inbox show a new incoming email while I'm already in yahoo mail?

None of the answers submitted even came close to answering what I asked. I've already clicked on inbox. Read my emails. I'm looking through the news. If a new email comes in it doesn't appear until I click on inbox again.
Why doesn't my inbox show a new incoming email while I'm already in yahoo mail?
Hi!!





Easy it is made that way!!! Sorry 2 bad :(!!!!





Hope I Help
Reply:Try clicking 'check mail".