What is wrong with it? Where can I manipulate my todo(s) via a web browser?
Update: Now the Android app stopped working too.
It got shut down, so you can’t access it anymore.
(Emphasis by me.)
And they recommend exporting your tasks and start using a different app.
It has already been shut down and we all have turned to other to-do app instead. Currently in the market, you have many choices. Some are even better than Astrid. I am using TickTick now and recommend you to have a try also. https://play.google.com/store/apps/details?id=com.ticktick.task