Help Needed. How can create a "mouse over event" on a map,

I have an old map of a town. I wish to scan it and have on a web page.

I then want markers on the map - and have a mouse over event to pop up a text box - dialogue box also clickable. The text box would have just a line or two of notes and click to access a page with more details of the buildings that were on that site

Might be the old way it was done, but I recall reading it was a Swedish? student who wrote the initial mouse over cursor over script.

If anyone can help I would appreciate it.