I want an image to repeat itself only on the x axis and start from the top left of a page. The image is a background of course.

background-repeat: repeat-x;

background: (color) (image) repeat-x top left;

replace color and image with what you want.

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All of the above. You can format it inside your stylesheet, or in the head of your page like this:

body {
background: url("image.jpg") repeat-x #fff;
}

You can change out "body" for any other element you want to put the background on. The reason the "#fff" is still in there is because when the background runs out, it needs to know what to fill the space with.

It's also advisable that you incorporate some positioning in there (like jolley_small did):

body {
background: url("image.jpg") top left repeat-x #fff;
}

"repeat-x" is interchangeable for "repeat-y" and "no-repeat" aswell. "top" and "left" can be interchanged with bottom, right, middle, or even values (like em, px, %, etc.).