When trying to get a dry erase marker off a dry erase board the best thing to use is glass cleaner. I use it all the time when cleaning mine. Its the same as taking the marker off the overhead...
If by "wet erase" markers you mean water-soluble markers, the answer is - usually yes. The surface preparation for dry erase boards (whiteboards) is different from the way you would prepare a surface...
The Question is not clear. Yo mean u want to delete the entire content of your web site or you want to erase the history of web site you visited. In what context you have asked this question?