This is my ad code
<IFRAME FRAMEBORDER=0 MARGINWIDTH=0 MARGINHEIGHT=0 SCROLLING=NO WIDTH=100% HEIGHT=90 SRC="http://ad.yieldads.com/st?ad_type=iframe&ad_size=728x90§ion=3824962&pub_url=${PUB_URL}"></IFRAME>
But when i put it in header it says its potentially harmful and i cant use it...???
You can't use ${PUB_URL} in templates as the current templating system uses eval() which is evil and is very risky so we black list certain patterns to help prevent arbitrary code execution.
So what next?? I've to compromise my earnings
Contact the company which you're using and ask them if there's a way to display advertisements without using ${PUB_URL}. If they say it's not possible, then you'd need to use an advertisement plugin (MyAdvertisements or My Ad Manager for example) which doesn't require code to be inserted in to the templates directly.