The image's width will be 400 pixels wide because that's the value defined in the stretchX CSS class. Return to your document and change 400 to any other value to make the image stretch to that width.

The percent-# class specifics the percentage width of the parent container an image should be. For example, percent-30 will make an image 30% the width of the parent. Percent classes can be applied in ...

Then I found out a quick and easy way to resize images with CSS by keeping your image’s aspect ratio. ... Second class will resize the images by keeping height as 300 pixels.

The class "col-md-4" instructs Bootstrap to make the content four columns wide, and "col-md-offset-4" tells Bootstrap to offset it by four columns, thus centering it. See Figure 6 for a rough overlay ...