Okay first, unless you have specific websites that are locked (Internal Government, Military, websites) in a particular code for a specific set of tasks that are very narrowally defines, IE10 and 11 (the current edition) will work on all websites normally. You can also use Google Chrome or Firefox alternatively, and that would resolve that issue, there shouldn't be a need to receed back and may just be a 'setting' or a update you didn't perform to make the website 'work'. We can go over those too to help instead of this backtrack.
That said, if your dead set to go back to Windows 7, you can either BUY a brand new copy (good luck not on store shelves) wiping the drive with DBAN first and starting clean OR as I noted, contact Lenovo and PAY for them to ship the Windows DVD for your laptop of course for a price. This can be also done via Support on thier website.
If any of this is too confusing, then please take it to a Mom & Pop Tech shop and explain the situation (including the websites your having issue with) and they can probably 'do it all for you' so you don't have to be overstressed by all the technical jargon / steps.