What kind of connection do you have?
Is your connection running ok, have a quick check of the modem or router to see that it is connected and running? ie have you posted on another persons computer to get help or are you using firefox or otherwise.
Can you give us some details about your computer its operating system etc, who provides your connection and what model of modem and router you use?
Also what other changes have you made in the last few days such as uninstalling installing or re-installing updates to programs. Things from up to a couple of days ago may have caused the problem so it helps to know so as to get to the bottom of it.
For a start have a go at using windows restore points to see if this clears it
click here is a step by step how to.