Generally, such error comes when we try to browse web-application url. There could be many problems around this problem and depends on it there are different solution for it.
First most common issue around this is that, web application does not contain any site collection at web application root level url, to resolve this you can create site collection from central admin ->Application Management ->Create Site Collection. During creation of site collection, please select your web application where you would like to create.
Second scenario, if you have already site collection created and still this problem occurs. To overcome such problem you have choice to restart IIS, reattach your content database, check services on your pc whether “work station” service is started.
Hope this will help!!