i think it should be entirely possible, at least for reading the internet. they would need a proxy in proximity of earth. like a satalite, or something buried in the earth, or hidden in our oceans, or drifting in the upper atmosphere, just so long as our Internet can reach it.
this would relay the information to their world which should take about 4.4 years to reach them if they live in Alpha Centauri.
as for putting up websites…well, they’d need to infiltrate our society in some way in order to have a web adress. i guess it should be possible, but if it’s operated from their home-world it takes 4.4 years to send anything to and 4.4 years to receive anything from there, so it would take 8.8 years for the site to respond to any changes that way. so it would have to be proxy-operated.
of course it also requires knowing at least one of our languages if we are to read it, and knowing how to code in uhm, what vika said. which, considering the 8.8 year delay, could really only be done by Visiters.