One common problem developers face while using master page that images did not get proper path, there are many ways to do this. But best way to use ResolveClientUrl . For example :
<img src=”<%= ResolveClientUrl(”images/disco_night.png”)%>” alt=”Disco night” />
after rendering it converted it as
<img src=”../images/disco_night.png” mce_src=”../images/disco_night.png” alt=”Disco night” />