How do I check what DNS servers I am using?
Look inside the router. Which one are you using?
If your Orange router is broken, they should replace it FOC.
In what way can't you access some websites? Does it come up with "Page not found" or time out? Then it is probably a DNS issue.
The boxes with red crosses are nothing to do with Orange. They are most likely broken links on the website you are on.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 17 Meg Untweaked 19 Meg Tweaked WBC