Problem with plugin MyAlerts

Hm, it seems that it broked your template, I think you should look at the MyAlerts template (carriage return, float in css ?). You could also have an error in your own template with an unclosed block for example, or the MyAlerts code is not put in the right place in your menu. The fact is MyAlerts introduced a block which broked your menu div.

You can also check your css there is not a conflict that could apply your own style to a MyAlerts block in a wrong way. There are many possible causes, to detect the problem the most convinient would be to use your browser debugger to check css of each block or to give a link where we could see the page.