iPad 4 , won't open page

[tigger0268]

When I try to open my kids online grade site it says the app is already open. I have no problem with this site on the iPad 1. The grade program opens a new tab for each new page. I go to the main site but then when it opens the login page on a new tab it says the app is already open and when I click ok it puts me back to the main site. HELP