We are always attracted to things that are free. But remember, you only get what you pay for and there is no such thing as a free lunch.
With so many people using the free server, there will be lots of competition. This means when someone tries to access your web page, it could take a long time. Most people tend to leave your site if your web page takes too long to load.
Free hosting does not really give you that much space on the server. At first it may seem lik a lot but once you start building your site, you will quickly see that you have no more room to add any new information.
With free hosting you do not get very many web tools to help you with your website. I had a free hosting where they did not allow me to FTP to my site. FTP is how you upload files to your web directories. I had to use their so called tools which took forever to upload, download or even make small changes to my web page. Also, you may not be allowed to use other script languages such as PHP or CGI scripts which help make your website more easy to navigate.
With free hosting they force you to have all these banners and advertisments and pop up windows which get very annoying to visitors. You have no control over this. Also, since it is free they will always try make you upgrade by paying for new hosting. They can even delete your account if they feel you are costing them money. I had a site on geocities. They closed this down but fortunately they gave some warning so I was able to download my web pages before they got deleted.
You get no help, or very little help, if you have problems with your site. Customer support is almost non-existent.
You cannot choose your own domain name. You have to follow a format they give you which often is not very related to what you really want. You are getting what is called a sub-domain which believe me, you will end up regretting.
Free hosting sites are very popular hacker targets. Hackers can deface your site, put porno on it, and even bring it down. In other words, with free hosting, you have no website protection and security. They can even cause you to be blacklisted by the major search engines.
As mentioned in many replies to your, free hosting is not reliable. Right after you spend months creating your site, they could go out of business. You are then, as they say, SOL.
Web hosting is really not that expensive, anywhere from $6 to $10 per month depending on the server space you need.
Before you dive into free hosting, really think about it. How are your class mates going to feel about you, if after all the hard work to make a website, your web hoster goes out of business, your site gets hacked, you have no more server space to add new information or your site gets crashed.
Remember, if it's too good to be true, it probably is.