I'm starting a project with bootstrap, but I can not adjust the mobile.
<div class="col-xs-12 col-lg-3 col-md-6 nopadding black appear ">
<img src="img/portfolio/thumbnails/1.jpg" class="thumb">
</div>
<div class="col-xs-12 col-lg-3 col-md-6 nopadding black appear ">
<img src="img/portfolio/thumbnails/1.jpg" class="thumb">
</div>
<div class="col-xs-12 col-lg-3 col-md-6 nopadding black appear ">
<img src="img/portfolio/thumbnails/1.jpg" class="thumb">
</div>
<div class="col-xs-12 col-lg-3 col-md-6 nopadding black appear ">
<img src="img/portfolio/thumbnails/1.jpg" class="thumb">
</div>
The cell phone recognizes the -md instead of -sm or -xs. I know that because of the current resolution of the devices, but how can I solve this?