Hi Adri

What did your size marker look like - was it bright and easy to see compared with your band?  If the marker was faint like your band, then there may be a problem with your stain quality or staining protocol.  If the marker was bright, then you probably don't have much DNA in your sample - how much sample did you load, and was it DNA or PCR product?   Was your gel prepared with stain (e.g. ethidium bromide), or did you stain your gel afterwards?  How old was the stain; is it stored away from light?  How much stain did you add relative to your gel size?  Add a picture of your gel to your question so we can see the problem. :)

You can always restart the current through a gel, your bands won't get blurry for several hours or even longer.  Just compare your samples to your controls and your ladder.

Like lucinda suggested, Look at your marker and see how bright or how expressed are the bands compared to your samples. Sometimes I run into this problem when I dont have a lot of DNA to start with, one way to go around it is add a little more EtBr it might help you detect your bands.