It looks like the link that has been copied and pasted across contains javascript.
As javascript within a link can be used to hack both the forum, the members account, or computer to do things such as XSS , XSRF luaching malware, etc. There are security filters within the forum that will strip out this type of code from within links, but if the hidden code is complex you may end up with an unusable link,
The person copy and pasting the link should use the 'Insert Hyperlink' button on the editor toolbar to add the link that way thus inserting a 'clean' link and not one that has javascript and other hidden code that could be malcious.