CSS float:left

So in the coding shown in the video :https://teamtreehouse.com/library/how-to-make-a-website/styling-web-pages-and-navigation/style-the-portfolio is so wrong ... I just cant manage to understand the problem He uses #gallery li even tho he was supposed to use only #gallery The coding he uses: #gallery li{ float::left; width:45%; margin:2.5%; background-color:#5f5f5f; color:#bdc3c7; } Is not applying any changes , when i remove li its still not working as show , im sure i spelled the id right and so on , but when i run the code its just 1 column instead of 2 , the first picture is smaller like it should be but there are no pictures in the right. Please help me , i cant move on with my track without it .