Answer: There are two instances where the web hosting provider inserts ads into your page.
Solution to 1 is to get paid hosting rather than free hosting. Some ISPs provide free web space as part of their connection service and restrict what you can use it for, others don't restrict you to personal sites but will insert ads as one of the conditions of making the space available "free".
Solution to 2 is to contact them and get them to remove the ads since if you are paying for the hosting then they have no right to insert their ads into your pages.
If you actually mean that your ISP is inserting ads into the pages you view and not your web hosting provider then the solution is to either switch to a different ISP oryou might try out different web browsers as their code may only be set to insert the ads in a specific browser. This latter is most likely to be the case if they supplied the browser (which would most likely be based on Internet Explorer).
This article written by Stephen Chapman, Felgall Pty Ltd.