Maybe there is no problem with the site itself, but I don't like advertising pop-up's at all - and pop-under's, that appear, when the browser is closed, even less. :(
Therefore is "red" the only suitable colour for that site.
Pls. excuse my poor English.
I think that the people who are leaving negative comments about this site are maybe not on the real William Hill site but instead on a scam version of this site. Be very careful and whatever you do don't give your bank or card details. I am using the real site and there are not any pop ups.