## Tell IE to use standards mode, not quirks mode
Define your doctype in your HTML:
element
See:
https://msdn.microsoft.com/en-us/library/cc288325(v=vs.85).aspx
## Tell IE to not use compatibility mode
This prevents, for example, IE 11 from using IE 7 rendering mode which can happen for many reasons.
If you can't add an HTTP header, then add this to your HTML and pray that it helps:
IE is using a compatibility mode if you see "compatible; MSIE" in the user agent header:
"Mozilla/4.0 (compatible; MSIE 7.0;"
See:
- http://stackoverflow.com/a/9338959
- https://msdn.microsoft.com/en-us/library/ff405803(v=vs.85).aspx
- https://blogs.msdn.microsoft.com/ieinternals/2013/09/21/internet-explorer-11s-many-user-agent-strings/
## Validate your HTML and CSS
https://validator.w3.org/
## Use an IE hack
Try "zoom" or "!important".