Over the salary cap

I saw a posting on this recently but can't find it. Is it OK to start the season over the salary cap (until I need to make roster moves)?
Also not sure how that happened. The LF I ranked was 750K salary but the draft gave me a $1.8M LF even though there were other undrafted LFs.
Also not sure how that happened. The LF I ranked was 750K salary but the draft gave me a $1.8M LF even though there were other undrafted LFs.