There are many hosting providers which provide the free web hosting. You do not need to pay anything to host your site on their server. Generally they put their ads in your website or place the popup or banner in your website. The free website hosts often make the money in other ways like putting the banners, popup or popup ads on your web pages. Some hosts do not place any ads or banners or popup but they are in hope that you may upgrade and pay for the advance features. Are free web hosts reliable?
Generally NO. Free web hosting is not reliable for the commercial use. Most of the free web hosts do not provide any kind of technical support for your website. You have to manage your site yourself. If the free web host allows anyone to signup and if they provide the features like PHP or CGI then some users may try to find way to abuse it, which cause the service interruption or it may possible that they need to shutdown the server which will lost your website as well as your data. You have to choose selective free web hosts which allow hosting only quality websites.
The best place to find the free web hosts is free web hosting directory. You will get the users review of the free web hosts from the web hosting directory. That may help you to choose the free host. Before you sign up for the free hosting, you have to check the disk space and bandwidth they provide. You need to go through their Terms of Services (TOS) before sign up.
It would be hard to recommend any free web host as different people need different web hosting features and most of the free web hosts provide different features. Free hosting is recommended for business. That means if your business depends on your web site then it is not recommend using free web hosting as generally they do not provide any kind of technical support and any uptime guarantee of the server.