Learn Responsive Design (Multiple Instruction Errors)

Hi guys and gals, just tinkering with the responsive design lessons to unrust my gears on CSS and HTML, I’m on Lesson 3, the one with the Space Travel web page.

I was told to insert this line of code so that the thumbnails resize depending on the minimum and maximum width of the screen:

@media only screen and (max-width: 480px) {
.page-title {
width: 270px;
}

}

@media only screen and (min-width: 320px) and (max-width: 480px) {
.gallery-item .thumbnail {
width: 95%;
}
}

However when I input these I don’t notice any change whatsoever in the browser, I resize it and the size just seems to stay the same across all the thumbnails… I kept bouncing between the code being there and not but the webpage just doesn’t seem to be altering in any way?

I keep finding errors in this course and reporting them but I want to know if anyone else is experiencing these issues?