I have seen this question popping up all over, so I thought I might write a small article about it.
The main reason for umbraco spitting out errors when you try to upload a file in the media section is a limitation of 4MB set in the file machine.config.
Normally, this file is off-limits if you are using shared hosting, but you can override it in your web.config file by inserting the following line inside the <system.web> section.
<httpRuntime maxRequestLength="size in kbytes" executionTimeout="time in seconds" />
For example, entering 8192 in maxRequestLength, will allow people to upload files of up to 8MB in size.
This should take care of the "Page cannot be displayed" or "Internet Explorer cannot display the webpage" error.