You are in the right forum, so no worries.
If this is a recent issue then their may be an intermittent issue in traffic routing elsewhere on the Internet, in which case it should clear itself after a bit (such things usually come and go with little notice and are often short lived).
In the meantime you should power off your WiFi and Cable/DSL modem for a minute or so then power them back on (cable/DSL modem first, followed by WiFi if they are separate devices). You may also wish to clear your web browser's cache (search on the web for instructions for your browser of choice) in case there is corrupt data in the cache that is causing issues with your web browser. You can also try rebooting the affected PCs as a failing operating system can exhibit strange behavior where some things work and others do not. It may also be caused by temporary interference with your WiFi connection as there are countless sources of interference that can degrade a WiFi network (microwaves, cell phones, Bluetooth, cordless phones, etc.) -- most of these sources will clear after a bit, though some can be long lived if the interfering signal is strong enough.
There is also a very small (rare) chance that a party previously using your present IP address may have attempted to attack this server, which may result in that IP, or a small block of IPs, being blocked for awhile. If that is the case then the simple act of cycling your Cable/DSL modem's power will usually result in a new IP address being issued to you, in which case that also resolves the access issue.
Do let us know if you continue to have problems after you have had a chance to try the above and some time has passed as these things often resolve themselves after awhile.
