If you are using IE, it sounds like you may have an option enabled to show you a message for every script error.
1.Use the Tools option from IE's menu bar to select "Internet Options".
2. In the "Internet Options" window, select the "advanced" tab.
3. Find the option "Display a notification about every script error". If it is selected, uncheck the box and restart IE.
A lot of these internet forums use JavaScript that isn't necessarily "perfect" for every browser. You can pretty much blame the browser vendors - yes all of them - (MS, Mozilla Org, Apple, etc...) for making that a difficult proposition.
If you can, use Firefox or Google Chrome and you'll have no problems with this site.