I didn't get the popup myself, which almost certainly means it's from Tripod; if I got it too, I'd be able to find it in the code and it would probably be consistent. If it's random behaviour, it's advertiser behaviour and that's the good people at Tripod.
Anyway, I will say this...for 15, it's not bad. For a lot of adults and even some professionals in this industry, it's not bad.
It's easy to navigate and the site looks relatively consistent throughout (although I would pick a default font and stick with it for the body).
My big issue with the site are those weird lines for the background. They don't really look right...they just look like random weird lines.
Another suggestion: learn Cascading Style Sheets (CSS). CSS will let you define fonts and layout styles for your HTML pages, keeping the style separate from the content and thus making it a buttload easier to maintain.
www.w3schools.com has a tutorial on CSS somewhere that you can learn and mess around with, or you may also want to try
www.lissaexplains.com (it's a teenager's way of explaining HTML and CSS to other teenagers and immature adults.)