Does anyone know what does it mean by start-tag and end-tag?
My browser keeps on saying that there's an error.
I'm not sure how to solve it.
This is xHTML standard where each tag should be closed.
In HTML, say you use <p>, you will close the tag with </p>. This is the mean of start-tag and end-tag.
In xHTML, every tag must be closed, eg <div></div>, <a></a>, etc. Some single tags like <br> and <img> are also require to close as <br /> and <img .... />
You can find more info in http://www.w3.org/TR/xhtml1/