Multiple wallets on one browser
Im using Chrome but on other browsers it should be same...
Browser holds in memory some data about your last login - session, so you have to open several incognito windows(CTRL+SHIFT+N chrome) or open several browser programs, by which I mean, one chrome, one IE, one mozzila. Becose every program has its own cache... But really easiest way is to open chrome and ten incognito windows with ctrl+shift+n...

so
for every wallet go to main page of CHROME browser CTRL+SHIFT+NEW will open incognito and type there blockchain.info